Massive props to www.Soundcloud.com for taking over as the new internet music engine.   I love it, easy to use, simple to follow and straight forward.  Themed in my favorite color, orange is very cool.  I am really digging the new beta layout and am ready for that to go full launch.  Soundcloud, you get two thumbs up from me!
     Basically you get with a free account, two hours of free storage, a profile, and friends network.  You can post tunes that you have made, dj sets, and even work in progress, share it among your friends or promote thru other social networks (facebook, twitter, forums and such) and listeners can easily navigate or skip around the track and leave comments.  Soundcloud has a great user back-end of the account to tally up all kinds of stats which I find very fun to dig into.  Also in the account is a dashboard with all the new material from friends you have added to your soundcloud network.  It takes a little time for this to get going but I have found some gems and instantly downloaded lots of great music off of this site.