It wouldn't hurt to collect a few into a larger collection - connected by genre, tone, theme or maybe even part of the same series. That way you can sell the shorter stories and still have it priced at Amazon's minimum of 99 cents.
I've heard conflicting reports about how well short fiction sells. I find my own collection sells pretty well - better than the novels, but at a lower price - but I think a part of that is because I can say "previously published" and "award nominated." It does make a difference to people - you might consider marketing the stories elsewhere first to gain a little cachet for them. (Also, when you publish a short story, your bio becomes an ad for your other work.)
To look for short fiction markets, I know of two sites:
The best is Ralan (
http://www.ralan.com/ ) but it's almost entirely for sf, horror, fantasy, paranormal and related genres. I've found quite a lot on Duotrope in other genres, but I haven't been marketing in a while.
http://www.duotrope.com
(Note, always check out the website of smaller and less established magazines to be sure they haven't closed or changed since they added a listing to ralan or duotrope.)
Camille