Edit: I'm at home... go to Edit->Preferences and choose the pane File Handling, in the lower part you have the Camera RAW Cache Settings where you can purge and select the directory.
Yeah, I found that option and moved my cache to my Lightroom drive. Jobodaho, I've been using a 16GB cache under the theory that bigger is better.
What seems to be taking up the most room is this Lightroom directory which gets installed on the same drive as Lightroom 2...
Lightroom 2 Catalog Previews.lrdata
At the moment, with cache cleared; this directory has 23GB of data in it which on my SSD is 33% of the formatted drive capacity. I have 10558 photos spread between a 50GB partition on the boot drive and a 75GB partition on the Lightroom drive which respectively take up 27GB and 47GB. So, after deleting all 10,600 previews (Library tab, previews, delete all previews), this directory still contains 10,600 files containing 23GB of data!