I was a big fan of Muxtape when it was alive and well, and these days it looks like 8Tracks is where it's at for online mixes. It bring in some social networking elements too - for example, you can "follow" people.
My good friend Mr. Chair was so thrilled about his new shower curtain that he was inspired to make a mix. And it's pretty damn good:
I'm also thrilled about Mr. Chair's new shower curtain, so much so that I was inspired to make a mix as well. And it's damn good: