I think I shall point you to the
Free SF Online Database, which is a round-up of links to full legal sf/fantasy works posted by their authors/publishers/as samples/promos online.
Always worth reading: just about anything by
- Ted Chiang (just plain brilliant, highly recommend his Stories of Your Life collection)
- Nancy Kress (often genetic engineering, also recommend her 3 paper collections)
- Connie Willis (wide range of marvelous stuff, 3-4 paper vy good collections; Fire Watch collection available as e-book)
- Judith Tarr (usually historical; well-written & well-researched)
- Robert J. Sawyer (mix of social and harder sf from a Canadian perspective; tends to go too jokey with the shorter stories, pick one of the award-winning novella-lengthers to start with, has 2 good paper collections)
- Terry Bisson (They're Made Out of Meat == Best Alien Contact Story EVER; Bears Discover Fire collection in DRM-free MultiFormat @ Fictionwise)
- Mike Resnick (quality varies, but usually funny to poignant; Kirinyaga collection @ Baen Webscriptions is excellent)
- James Patrick Kelly (inventive and sometimes disturbing),
and no doubt many more that others will suggest.
Also, I should note that Small Beer Press is offering
a few of their authors works under a Creative Commons license, in various e-reader friendly formats contributed by site visitors.
I especially recommend Maureen McHugh's Mothers and Other Monsters, which I went so far as to buy in paperback. Okay, that happened long before I even knew there was an online version. But the point is, her work is good enough for me to special-order my own copies of it.