It's not unusual for authors to put excerpts of their work online. It gives the writers an opportunity to attract new readers and gives their established fans a taste of what's to come. Below are a few such sites. I'll post more as I come across them.Writers and Readers, if you know of others please let me know.
From Caridad Piniero: "This Wicked Wednesday brings something totally new — a work in progress. I’ve been developing an urban fantasy involving a twist to the werewolf mythology, battles with vampires and a struggle for control in a werewolf pack. The tentative title is Undead Uprising. " Eight chapters are available for your reading pleasure.
Read an excerpt of Vampire Interrupted by Lynsay Sands. (Avon, March 2008).
Chapter one of Laurell K. Hamilton's new Anita Blake adventure, Blood Noir (Berkley May 27, 2008) is available.
Rachel Caine offers a sample chapter of Feast of Fools (The Morganville Vampires, Book 4) Signet, 2008
On Joey W. Hill's site find an excerpt of her erotic romance Mark of the Vampire Queen (Berkley February, 2008).