Sluggy Freelance is a web comic that has been running since August 25, 1997. The comics are organized into books and chapters online, and several paper books have been printed. The books are as follows:
Book 1: Is It Not Nifty?
Book 2: Worship the Comic
Book 3: When Holidays Attack!
Book 4: Game Called on Account of Naked Chick
Book 5: Yippy Skippy, The Evil!
Book 6: The Bug, the Witch, and the Robot
Book 7: A Very Big Bang!
Book 8: Fire and Rain
Many of the later comics online are not yet included in books.
Sources: books listed above by Pete Abrams, and http://sluggy.com