Baen periodically releases books in DRM-free ereader format... for free.

http://www.baenebooks.com/c-1-free-library.aspx
Some examples (but nowhere near all inclusive):
1632 - Eric Flint
The Tank Lords - David Drake
On Basilisk Station - David Weber
Retief! - Keith Laumer
Star Soldiers - Andre Norton
The Road to Damascus - (A BOLO novel) John Ringo & Linda Evans
Have fun. You can curse me for your lost productivity later.

Edit: Should mention, you don't really need an ereader. When they release 'em they include an HTML version too. You can just read 'em online if you want.
Here's March Upcountry (which is excellent by the way)
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"Any sufficiently advanced idiocy is
indistinguishable from trolling." -- Arthur C Clarke


