Found out about a site this week - Centsless Books that lists books available for free on Amazon. Apparently the list is updated hourly. Here is the sci-fi list. Now I see some pretty good stuff here that is available other ways - via Baen or Gutenburg for example. But if you have a kindle it is rather handy.
I'm reading Drake's "Redliners" right now and I'm enjoying it immensely. But I've always been partial to his military sci-fi. I love all the Hammer's Slammers stuff and such. Anyway - it's a handy site that I thought some of you might enjoy.