I buy from Baen
, and a handful of individual author sites & tiny publishers. I don't buy DRM'd ebooks. (At the moment, I don't even download free DRM'd ebooks, but that's because about six months ago I got a new computer, and I'm not yet up to dealing with DRM software. I'll probably eventually decide it's worth the hassle.)
I get free books from mobileread forums, feedbooks
, the Baen free library
, fanfiction websites like the fanfic ebook library
, individual author sites, publisher promos like the Harlequin freebies
, Smashwords, and Project Gutenberg
. I don't tend to get them from Munseys
because I'm not fond of the site interface, and there's a lot of overlap w/feedbooks & gutenberg.
I'm vaguely looking for sources of free or cheap manga, but only vaguely, because I'm not strongly interested and I'm nowhere near running out of free stuff I want to read.