I'm not a huge SciFi fan to begin with, but I happen to know that the Baen Free Library (http://www.baen.com/library/) is an excellent resource for free SF ebooks. The rest of the Baen site has pay books.
Oh, and who doesn't love Fictionwise (http://www.fictionwise.com)?
I started this as a new thread so people could post their favorite SF links here, too. so please add yours!

The best source ( IMHO ) is the usenet : alt.binaries.e-book.palm
Have a look, you wont be disappointed...

Originally posted by AlexisV
The best source ( IMHO ) is the usenet : alt.binaries.e-book.palm
Have a look, you wont be disappointed... Yeah, but those are pirated, illegal copies of e-books...not public domain (for the most part). To each his own, as far as downloading warez files, but just wanted members to be aware that alt.binaries.e-book.palm is a mostly-warez newsgroup.