I'll be digging through these sites for some new reading material, you can bet on that…
Baen Free Library
You’ll find around a hundred or so free ebooks here. There’s also an Annotated Baen Free eBook Listing, which includes scads of CD-ROMs that shipped as promotional materials, all neatly zipped up for download.
Cory Doctorow has made gobs of his science fiction novels and novellas available online for download. I enjoyed Little Brother, though fans of classic space opera are likely to be left somewhat mystified.
Nearly 500 DRM-free science fiction ebooks, most of which are new to me, for good or ill. Ratings from the community should help both the visitor and myself to judge what might be worth downloading.