This is a simple to setup site for selling/giving away while building a mailing list: PDF's, tickets, videos, music and subscriptions.
My uncle asked me how to sell a book on-line so I did some research and sent his a quick list of resources he could check. I thought it would make a good blog post too.
1. Selling for Amazon - Being an affiliate is easy to signup for. I am one and maintain a book store at http://www.geekzonebooks.com
(Scroll down untill you see the book store section)
More Info: https://affiliate-program.amazon.com/
2.Selling on Amazon - Once you have a book either hardcopy or kindle e-book formatted you can sell it on Amazon. You will need your ISBN Number and Barcode established here: http://www.bowker.com/en-US/products/servident_default.shtml
More info: http://www.amazon.com/gp/seller-account/mm-summary-page.html?ie=UTF8&ld=AZFooterSelfPublish&topic=200260520
3. Directly selling your self published book through CafePress.Com is easy once you have your book in PDF format. See my shop there: http://www.cafepress.com/wwwmtbnnet
4. Another good site to directly sell you PDF through is GumRoad. I have a site up there at this url:
5. If you have information that changes on a regular basis then maintaining a blog may be a good option. For example if you built a following of people who watch what you are buying/selling you could do your trade each day and then post a announcement about it to your blog and your subscribers would then follow your lead. I don't know if having a bunch of people do what you do right after you do it would be a good thing but if it would be then building a large following of other day traders would be good for marketing your books to once they trust your trades to be well researched. I build blogs for authors. Check my latest one out: http://www.danamanciagli.com/