Fixed is fun, but I'm on a single speed kick this season. I found myself really missing bunny hopping last year and since I want to race cross this fall I definitely need the practice. My IRO Rob Roy frame is on the way and that's going to be built up on a single fixed hub (but with a freewheel for '07 at least).
This will also give me a chance to learn trackstands on a freewheel bike ... so far I'm still doing cheater trackstands (inching forward instead of staying still/rocking back and forth).