http://en.wikipedia.org/wiki/Comparison_of_e-book_formats
http://www.engadget.com/tag/EBookReader/
.epub (burgeoning standard with weak drm)
.lit (Microsoft Reader with weak drm)
.pdf (Adobe)
.AZW (Kindle with drm)
.pdb (>_> B&N with drm)
.html (no drm, can usually convert to anything)
.lrf (Sony's failed format, replaced by Adobe version of .epub I believe)
.imp (ebookwise, fictionwise)
.prc (mobipocket)
All of the above, including .lit, now or will soon have an ebook reader for the format.
The burgeoning standard is .epub. There is a DRM'ed version by Adobe (i think). The problem is, epub DRM was made only to prevent casual copying (stupid, idiotic, foolish move that hurts the innocent consumer, yet can be broken and shared by those with the know-how) and can be broken.
Epub is reflowable-
http://www.teleread.org/2009/02/16/...nd-others-in-addition-to-apps-such-as-stanza/
"Reflowable PDF means that line lengths can more easily fit the size of the screen"
Some small ebook publishers release in every format you could want without DRM.
Ebook piracy exists and seems to have been around for a while. I assume that nowadays they just break the DRM if they can, but there are book scanning machines that they may use.
