Muxtape- DIY digital, no cassette required
Among the many places where you can not only share (or show off) your favorite songs and actually have people listen to them is Muxtape. You can browse through your MP3 collection and add 12 files/songs that are each less than 10MB and viola, instant digital mixtape of whatever you want now. I set one up here:
You can sign up for free and set up your own too. That is, until the site gets shut down... so enjoy it now.
Thanks to Tim Broun for hipping me to this.