Give OmniDiskSweeper a try - it will scan your hard drive and show you exactly what's taking up all your space.
Thanks for the reminder, I just reclaimed 5GB of caches on my MacBook.Likely one of your logs got out of control.
Try an Onyx run - see if that clears it.
This may help you find it.
Disk Inventory X 1.0 - Mac OS X - VersionTracker