I managed to stumble upon an entire forum for Kindle freaks like myself: http://www.kindleboards.com/. Within that forum I found a couple of handy links that can help you decide what you would like to read next. I always figured there had to be a website out there that you could put in a favorite author and/or book and come back with suggestions...well here you go:

http://www.whatshouldireadnext.com/search
http://www.gnooks.com/
http://www.literature-map.com/ "map" your favorite author! See who else is close.
http://www.allreaders.com/ - Search for books by plot.

Additionally, free ebook sites....
http://feedbooks.com/
http://freekindlebooks.org/
http://www.gutenberg.org/wiki/Main_Page
http://manybooks.net/
http://www.baen.com/library/ (Science fiction)
http://www.kindleclassics.org/

Woo! Happy Reading :)