Also - while most apps do a pretty good job of cleaning up their work files when you quit them, they're not all 100 percent perfect all the time, and most can lose a file once in a while if the system crashes (fortunately rare with OS X). Do a Spotlight search for files with "work file" in their names and delete them. Then search for files with "temp" in their names and check those for deletability, too. Most files you get this way will be small, but, depending on what you've been working on, some may be large enough to notice.