So all of a sudden, I went from having roughly 30-40G free to 200MB free on my hard drive. I earlier had used iSquint to attempt a video conversion. Later on, I noticed in Activity Monitor that ffmpeg was using close to 100% of the CPU. Eek! I realized it was eating my hard drive space, and so I went hunting to find the huge file... lo and behold, WhatSize showed that /private/tmp/isquint_time was the culprit at 34.4GB!! So just a word of warning to you iSquint users... if you notice hard drive space filing up fast, check Activity Monitor and look for that file.