Margaret Weis

Sovereign Stone Trilogy with Tracy Hickman
Well of Darkness
Guardians of the Lost
Journey into the Void

Kathy Reichs

Temperance Brennan
1. Deja Dead (read pre-blogging)
2. Death Du Jour (read pre-blogging)
3. Deadly Decisions (read pre-blogging)
4. Fatal Voyage (read pre-blogging)
5. Grave Secrets (read pre-blogging)
6. Bare Bones 
7. Monday Mourning
8. Cross Bones 
9. Break No Bones 
10. Bones to Ashes 
11. Devil Bones 
12. 206 Bones
13. Spider Bones
14. Flash and Bones
15. Bones are Forever
16. Bones of the Lost
17. Bones Never Lie
18. Speaking in Bones

Virals
1. Virals
2. Seizure
3. Code
4. Exposure
5. Terminal

Jane Langton

Hall Family Chronicles

The Diamond in the Window
The Swing in the Summerhouse
The Astonishing Stereoscope
The Fledgling*
The Fragile Flag
The Time Bike
The Mysterious Circus
The Dragon Tree (2008)

Homer Kelly Mysteries

The Transcendental Murder
Dark Nantucket Noon*
The Memorial Hall Murder
Natural Enemy
Emily Dickinson Is Dead
Good and Dead
Murder at the Gardner
The Dante Game
God in Concord
Divine Inspiration
The Shortest Day: Murder at the Revels
Dead as a Dodo
The Face on the Wall
The Thief of Venice
Murder at Monticello
The Escher Twist
The Deserter: Murder at Gettysburg
Steeplechase

Mercedes Lackey

Fairy Tale

1. Firebird (read pre-blog)
2. The Black Swan (read pre-blog)

Bard's Tale

1. Castle of Deception (read pre-blog)
2. Fortress of Frost and Fire (read pre-blog)
3. Prison of Souls (read pre-blog)
4. The Chaos Gate by Josepha Sherman
5. Escape From Roksamur by Mark Shepherd
by Holly Lisle:
Thunder of the Captains (1996)
Wrath of the Princes (1997)
Curse of the Black Huron (1998

Elemental Masters

1. The Fire Rose
2. The Serpent's Shadow (read pre-blog)
3. The Gates of Sleep (read pre-blog)
4. Phoenix and Ashes (read pre-blog)
5. The Wizard of London
6. Reserved for the Cat
7. Unnatural Issue
8. Home From the Sea (tbp June, 2012)

Valdemar

After a lot of googling, everything I've read says it's best to read the books in the order they were published. So I've come up with this list that is chronological by publishing date but keeps trilogies together. If you are a fan and think I've made a grave error in order here somewhere please let me know.

Arrows of the Queen, 1987
Arrow's Flight, 1987
Arrow's Fall, 1988

Magic's Pawn, 1989
Magic's Promise, 1989
Magic's Price, 1990

The Oathbound 1989
Oathbreakers 1989
Oathblood 1989

By the Sword 1991

Winds of Fate, 1991
Winds of Change, 1992
Winds of Fury, 1993

Storm Warning, 1994
Storm Rising, 1995
Storm Breaking, 1996

The Black Gryphon 1994
The White Gryphon 1995
The Silver Gryphon 1996

Sword of Ice And Other Tales of Valdemar, 1997

Owlflight, 1997
Owlsight, 1998
Owlknight, 1999

Brightly Burning 2000

Exile's Honor, 2002
Exile's Valor, 2003
Take a Thief, 2004

Sun in Glory And Other Tales of Valdemar 2003
Crossroads And Other Tales of Valdemar, 2005

Moving Targets and Other Tales of Valdemar, 2008

Foundation (2008)
Intrigues (2010)
Changes (2011)

Changing the World: All New Tales of Valdemar (edited by mercedes Lackey) (2009)
Finding the Way and other tales of Valdemar (2010)

Margaret Peterson Haddix

Shadow Children

1. Among the Hidden (1998)*
2. Among the Imposters (2001)*
3. Among the Betrayed (2002)
4. Among the Barons (2003)
5. Among the Brave (2004)
6. Among The Enemy (2005)
7. Among the Free (2006

Debi Gliori

Pure Dead

1. Pure Dead Magic (read July, 2007)
2. Pure Dead Wicked (read Sept. 2007)
3. Pure Dead Brilliant
4. Deep Trouble aka Pure Dead Trouble
5. Deep Water aka Pure Dead Batty
6. Deep Fear aka Pure Dead Frozen

Colleen Gleason

Gardella Vampire Chronicles

1. The Rest Falls Away (read Sept, 2007)
2. Rises the Night (read Sept, 2007)
3. The Bleeding Dusk (read July 2008)
4. When Twilight Burns (read Nov. 2008)
5. As Shadows Fade