Cacheman is a Windows app from Outer Technologies that's "designed to improve the performance of your computer by optimizing the disk cache, memory and a number of other settings." In addition to helping you tweak some settings to give your computer a little boost, Cacheman also has a great memory recovery mode that'll monitor your computer's memory use and, when it's running low, shuffle things around in RAM and free up anywhere from (in my experience) 10-50MB of physical memory. For that feature alone Cacheman is worth it's weight in gold, but fortunately for us software doesn't weigh anything and Cacheman is free.