(Listed first by category, then alphabetically by author)

Best teen fiction released in 2008:
What Happens Here by Tara Altebrando
The Fortunes of Indigo Skye by Deb Caletti
Looks by Madeleine George
Poison Ink by Christopher Golden
Soulless by Christopher Golden
Paper Towns by John Green
Forever Changes by Brendan Halpin
Girl Overboard by Justina Chen Headley
Suite Scarlett by Maureen Johnson
Love (and Other Uses for Duct Tape) by Carrie Jones
Feathered by Laura Kasischke
The Disreputable History of Frankie Landau-Banks by E. Lockhart
On the Jellicoe Road by Melina Marchetta
The Adoration of Jenna Fox by Mary E. Pearson
Black Box by Julie Schumacher
Living Dead Girl by Elizabeth Scott
High Dive by Tammar Stein
Cracked Up to Be by Courtney Summers
A Little Friendly Advice by Siobhan Vivian
Sweethearts by Sara Zarr

Notable debuts in teen fiction:
Audrey, Wait! by Robin Benway
Band Geek Love by Josie Bloss
Read My Lips by Teri Brown
Shift by Jennifer Bradbury
She's So Money by Cherry Cheva
Oh. My. Gods. by Tera Lynn Childs
Jump the Cracks by Stacy DeKeyser
The Opposite of Invisible by Liz Gallagher
Looks by Madeleine George
Stray by Stacey Goldblatt
Everything Beautiful in the World by Lisa Levchuk
The Comeback Season by Jennifer E. Smith
The Shape of Water by Anne Spollen
Cracked Up to Be by Courtney Summers
A Little Friendly Advice by Siobhan Vivian
Good Enough by Paula Yoo

Additional notable teen releases:
Wish You Were Here by Catherine Clark
Prom Kings and Drama Queens by Dorian Cirrone
a href="http://slayground.livejournal.com/331914.html">Lock and Key by Sarah Dessen
The Year My Sister Got Lucky by Aimee Friedman
House of Dance by Beth Kephart
How to Ditch Your Fairy by Justine Larbalestier
How They Met, and Other Stories by David Levithan
Geek Magnet by Kieran Scott

Best juvenile fiction released in 2008:
Tennyson by Lesley M.M. Blume
The Patron Saint of Butterflies by Cecilia Galante
The Life and Crimes of Bernetta Wallflower by Lisa Graff
Palace of Mirrors by Margaret Peterson Haddix
Violet Raines Almost Got Struck by Lightning by Danette Haworth
Toy Dance Party: Being the Further Adventures of a Bossyboots Stingray, a Courageous Buffalo, and a Hopeful Round Someone Called Plastic by Emily Jenkins, illustrated by Paul O. Zelinsky
Savvy by Ingrid Law
Jessie's Mountain by Kerry Madden
Judy Moody Goes to College by Megan McDonald, illustrated by Peter Reynolds
My So-Called Family by Courtney Sheinmel

Notable debuts in juvenile fiction:
Hershey Herself by Cecilia Galante
Violet Raines Almost Got Struck by Lightning by Danette Haworth
Savvy by Ingrid Law
My So-Called Family by Courtney Sheinmel

Authors entering new territory: (writing for a new genre or age group)
You Know Where to Find Me by Rachel Cohn
The Ashleys by Melissa de la Cruz
Sunny Holiday by Coleen Murtagh Paratore (technically, this is a January 2009 release, but it was already available in December)
The Adoration of Jenna Fox by Mary E. Pearson
A Kiss Before the Apocalypse by Thomas E. Sniegoski (his first solo adult novel)
The Shape of Water by Anne Spollen
The Floating Circus by Tracie Vaughn Zimmer

Best second or third releases:
Ten Things I Hate About Me by Randa Abdel-Fattah (technically, this is a January 2009 release, but it was already available in December)
Tennyson by Lesley M.M. Blume
Prom Kings and Drama Queens by Dorian Cirrone
No Cream Puffs by Karen Day
Nothing by Robin Friedman
The Life and Crimes of Bernetta Wallflower by Lisa Graff
Paper Towns by John Green
Girl Overboard by Justina Chen Headley
Itch by Michelle D. Kwasney
On the Jellicoe Road by Melina Marchetta
How to Build a House by Dana Reinhardt
High Dive by Tammar Stein
Crimes of the Sarahs by Kristen Tracy
Leftovers by Laura Wiess
Sweethearts by Sara Zarr

Best picture books of 2008:
Seamore, the Very Forgetful Porpoise by Darcie Edgemon, illustrated by J.otto Siebold
Mermaid Sister by Mary Ann Fraser
Wave by Suzy Lee
Gone Fishing by David McLimans
South by Patrick McDonnell
A Kitten Tale by Eric Rohmann
Dog and Bear: Two's Company written and illustrated by Laura Vaccaro Seeger
Peg Leg Peke by Brie Spangler

Notable graphic novels:
BSC Graphix: Claudia and Mean Janine by Ann M. Martin and Raina Telgemeier
Rapunzel's Revenge written by Shannon Hale and Dean Hale, illustrated by Nathan Hale
Coraline graphic novel adapted and illustrated by P. Craig Russell, based on the novel by Neil Gaiman

Most promising new juvenile series:
Suddenly Supernatural by Elizabeth Cody Kimmel (#1: School Spirit)
The Brimstone Network by Tom Sniegoski (#1: The Brimstone Network; #2: The Shroud of A'Ranka)

Best continuing juvenile series:
Zibby Payne series by Alison Bell (newest release: #5: Zibby Payne and the Red Carpet Revolt)
In the Cards trilogy by Mariah Fredericks (conclusion: #3: Life)
Just Grace books by Charise Mericle Harper (newest release: #3: Just Grace Walks the Dog)
Babymouse by Jennifer L. Holm and Matthew Holm (graphic novels; newest release: #9: Monster Mash)
The Maggie Valley books by Kerry Madden (newest release: Jessie's Mountain, which may or may not be the conclusion)
Judy Moody books by Megan McDonald, illustrated by Peter Reynolds (newest release: #8: Judy Moody Goes to College)
Stink books by Megan McDonald, illustrated by Peter Reynolds (newest release: #3: Stink and the Great Guinea Pig Express)
Owlboy by Thomas E. Sniegoski, illustrated by Eric Powell (newest release: #4: The Flock of Fury)
Hollywood Sisters series by Mary Wilcox (newest release: #4: Star Quality)
The Disney Fairies series by various authors

Notable sequels in juvenile or teen fiction:
The Penderwicks on Gardam Street by Jeanne Birdsall (sequel to The Penderwicks)
Palace of Mirrors by Margaret Peterson Haddix (companion to Just Ella)
Toy Dance Party: Being the Further Adventures of a Bossyboots Stingray, a Courageous Buffalo, and a Hopeful Round Someone Called Plastic by Emily Jenkins, illustrated by Paul O. Zelinsky (sequel to Toys Go Out)
Love (and Other Uses for Duct Tape) by Carrie Jones (sequel to Tips on Having a Gay (Ex) Boyfriend)
Flora's Dare: How a Girl of Spirit Gambles All to Expand Her Vocabulary, Confront a Bouncing Boy Terror, and Try to Save Califa From a Shaky Doom (Despite Being Confined to Her Room) by Ysabeau S. Wilce (sequel to Flora Segunda)

Most promising new teen series:
Lucky by Rachel Vail (the first in a planned trilogy)

Best continuing teen series:
Pretty Little Liars by Sara Shepard (newest release: #5: Wicked)

Most promising new fantasy series for adults:
The Hidden Cities books by Christopher Golden and Tim Lebbon (First book: Mind the Gap; second book, The Map of Moments, coming in January 2009)
The Remy Chandler books by Thomas E. Sniegoski (First book: A Kiss Before the Apocalypse; second book, Dancing on the Head of a Pin, coming in April 2009)

Best conclusions to fantasy series for adults:
The Lost Ones: Book Three of The Veil by Christopher Golden

Notable non-fiction for teens, families, and big readers:
Things That Make Us [Sic] by Martha Brockenbrough
Prince of Stories: The Many Worlds of Neil Gaiman by Hank Wagner, Christopher Golden, and Stephen R. Bisette You're Amazing! A No-Pressure Guide to Being Your Best Self by Claire Mysko
Chill: Stress-Reducing Techniques for a More Balanced, Peaceful You by Deborah Reber

Best backlist picture books read in 2008:
Mrs. Marlowe's Mice by Frank Asch and Devin Asch
Alphabeasts by Wallace Edwards
The Incredible Book-Eating Boy by Oliver Jeffers
The Cinder-Eyed Cats by Eric Rohmann
Cookies: Bite-Size Life Lessons by Amy Krouse Rosenthal, illustrated by Jane Dyer
Dog and Bear written and illustrated by Laura Vaccaro Seeger
Bella Gets Her Skates On by Ian Whybrow, illustrated by Rosie Reeve

Best backlist juvenile books read in 2008:
Toys Go Out: Being the Adventures of a Knowledgeable Stingray, a Toughy Little Buffalo, and Someone Called Plastic by Emily Jenkins, illustrated by Paul O. Zelinsky
The Julie books by Megan McDonald, illustrated by Robert Hunt (six books in the series; part of American Girl)
Good Luck, Ivy by Lisa Yee, illustrated by Robert Hunt

Best backlist young adult books read in 2008:
The Poison Apples by Lily Archer
Many Stones by Carolyn Coman
Lush by Natasha Friend
The Secret Life of Sparrow Delaney by Suzanne Harper
Undercover by Beth Kephart
The Decoding of Lana Morris by Laura McNeal and Tom McNeal
Marie, Dancing by Carolyn Meyer
Kissing Kate by Lauren Myracle
Song of the Sparrow by Lisa Ann Sandell
Hacking Harvard by Robin Wasserman

Best backlist graphic novels read in 2008:
Robot Dreams by Sara Varon

Best backlist adult novels read in 2008:
The Life Before Her Eyes by Laura Kasischke

Notable advance reads in teen fiction: (in order of publication)
Ten Things I Hate About Me by Randa Abdel-Fattah (coming out in January 2009)
North of Beautiful by Justina Chen Headley (February 2009)
My Life from Air Bras to Zits by Barbara Haworth-Attard (February 2009)
Same Difference by Siobhan Vivian (March 2009)
Something, Maybe by Elizabeth Scott (March 2009)
This is What I Want to Tell You by Heather Duffy Stone (March 2009)
Band Geeked Out by Josie Bloss (April 2009; sequel to Band Geek Love)
Purge by Sarah Darer Littman (April 2009)
After the Moment by Garret Freymann-Weyr (May 2009)
The Waking (previously known as Gaijin Girl), Book One: Dreams of the Dead by Thomas Randall (teen fiction, fall 2009)
The Waking, Book Two: Spirits of the Noh by Thomas Randall (teen fiction, late 2009)

Outside links:
My select list of Best Books of 2008 on Amazon
My select list of Best Books of 2009 (So Far) on Amazon

From the Bildungsroman Archives:
Best Books of 2007
Best Books of 2006
Best Books of 2005