8tracks
A good mixtape can say so many things -- you've got a powerful radar for unknown bands, you've got a powerful radar for hair metal, you want to make out -- but the message is always undermined by an awkward exchange that leaves the giftee thinking you want to make out. Send a link instead, with 8tracks.
For spreading your mix to everyone, 8 lets you embed its player in your blog/site/MySpace page -- so the only thing standing between you and some righteous heavy petting is the awkward revelation that you actually have a MySpace page.
