What should I put in my Slot 1?

Currently I have a wonderful Pentium II at 333 MHz, it's really cool, and allows me to run it fanless (I'm waiting for a new 5600 RPM 2.5" HD, which will hopefully make my case completely silent -- the PSU fan is already silent, and I stripped everything else out) -- what could I replace it with?  Should I replace it?

In before ``put it in''.