A little while ago, I shared some thoughts on two of my favourite 'internet radio' sites. Since writing that post, I've discovered a new 'PRO' for each service:
Mixcloud: They've just announced the release of their iPhone app. And it is free… for now (it sounds like it might not always be free, so get on it now if your pocket change is heavy on the lint side). This is a pretty huge step up for the awesomeness of their service. Especially if you have an iPhone.
8tracks: You can add your own buy links for a track on your mix (perhaps this has always been the case, but I just noticed it recently). If you've never made a mix on 8tracks before, a buy link is automatically found for any track you upload, usually from Amazon (Mixcloud does this too). This works fine for when you are using a more established artists track in your mix, but a lot of artists / tracks are not available on Amazon. 8tracks allows you to add your own link (i.e. to Bandcamp, or Soundcloud, or even to the artists website). This is a big plus for smaller artists who get their music featured on a mix but are not on any of the big online distributors (as long as the creator of the mix takes the little extra time in adding the link).