Sounds like the SciFi site would be:
http://www.baen.com
Ectaco provided these on a card with the JBL:
http://www.ereader.com/
http://www.fictionwise.com/
Free eBooks at:
http://www.feedbooks.com/
http://www.manybooks.net/
http://www.gutenberg.org
Then there are
http://www.smashwords.com/
For as long as the USENET survives there are a few binary Newsgroups that have
ebooks for download. (search for groups with "ebook" in their name)
alt.binaries.e-book.palm or alt.binaries.e-books.palm for instance.
Luck;
Ken