If you haven't read Westerfeld, I like to describe him as the Joss Whedon of literature. Which should tell you right away whether you will enjoy reading his stuff or not. Not quite complete - but almost:
Polymorph (1997) - Still missing this one, can be hard to find. Fine Prey (1998) Evolution's Darling (2000) So Yesterday (2004)
Succession series
The Risen Empire (2003) The Killing of Worlds (2003)
Midnighters trilogy
The Secret Hour (2004) Touching Darkness (2005) Blue Noon (2006)
Polymorph (1997) - Still missing this one, can be hard to find.
Fine Prey (1998)
Evolution's Darling (2000)
So Yesterday (2004)
Succession series
The Risen Empire (2003)
The Killing of Worlds (2003)
Midnighters trilogy
The Secret Hour (2004)
Touching Darkness (2005)
Blue Noon (2006)
Uglies series
Uglies (2005)
Pretties (2005)
Specials (2006)
Extras (2007)
Peeps series
Peeps (2005)
The Last Days (2006)
Leviathan series
Leviathan (October 6, 2009)
Behemoth (October 5, 2010)
Goliath (September 20, 2011)