You can do two things with 8tracks, either stream mixes or create your own. As it works under a radio licence there are some caveats on what you can include on your mix (no more than two tracks from one album, random playback order, and no information on what the next track will be), but once you upload and create a mix (which you need your desktop browser for) you'll be able to listen back to it on your Windows Phone.
It's also shared out so anyone browsing 8tracks by tag or name can find a mix that other members have shared publicly. The great thing here is that all the mixes have been created by users, there's no computer extrapolation here. This "hand crafted" environment makes browsing 8tracks pretty fun. As you'd hope, it uses the regular Windows Phone media controls, and mixes will appear in the history pane in music+video.
You can sign up in the app or through the 8tracks website, and download the Windows Phone application direct from AAWP.