I've been using this for some time. It really does give a small boost specially on my 2006 vintage laptop with only 1 gig ram. The new versions also work in vista.
"Give Your Windows PC a Boost! eBoostr™, working as an alternative solution to ReadyBoost and SuperFetch technologies, implements a different advanced approach to use flash memory to speed up your computer It speeds up your PC and improves application responsiveness by using flash memory and free RAM as an extra layer of performance-boosting cache for your PC. Use up to four inexpensive flash devices to speed up your system. Add more speed to your PC without any hardware upgrade!"
- Boost your Windows PC performance » eBoostr.com (view on Google Sidewiki)