Mobipocket have an excellent (and free -- adding to the excellence :wink
e-book creation program called Mobipocket Creator. It generates .PRC files that can be read in their freeware reader, and can make them from PDFs, DOC files, Web pages, you name it.
http://www.mobipocket.com
They also have a store for e-books, but I haven't bothered with that. I just give my e-books away from my site (hamishmacdonald.com), from ManyBooks.net (whose designer can whip your book into every conceivable electronic form known to man using the scripts he's created), and on Memoware.com.
My second novel has been downloaded 2,306 times from Memoware, but I've never heard from a single person about it, so I'm not sure what the business model is for e-books or whether it relates to any real sales. Someone I knew a while back said publicly that his free e-books drive sales of his physical books, but then, he's won the Hugo award more times than I've had pizza, so it's different for him.
I figure I've got a day-job, so my aim in publishing is to find my audience of readers, not to concentrate on bagging income. But if the teaser PDF thing works for you, more power to you.