bandcamp.com is incredibly handy for online downloads. anyone who downloads off of the site can download the songs in whatever file format they want, from mp3 to flac..
just you can't upload mp3s to the site.. because an mp3 converted to flac just isn't kosher
also, you get 200 free download codes when you make the page, and you can get 500 for $15 or 1000 for $20
With Weirdonia on this one...Bandcamp offer an excellent service....as well as free or fixed price downloads you can set name your own price downloads with or without a minimum figure...(but watch out for PayPal's minimum transaction cost)...you can also bundle tracks into "albums" and include artwork and videos and stuff in the download....