Windows Vista contains a performance booster functionality called ReadyBoost which really can improve the performance of your Windows Vista system. In fact, ReadyBoost, is one of the top five Windows Vista features according to Ed Bott.
In short ReadyBoost caches programs on a flash drive to speed up your Vista, reports are that a program that previously started in 10 seconds will now start in 2-4 seconds.
Almost all articles I have read on this subject says that you should use an USB-stick as your ReadyBoost flash drive, but it will work with any kind of flash drive, like an SD-card.
Using an SD card is for me much more better since I have an Dell XPS m1210 laptop. Having an USB-stick pointing out will almost certainly destroy the stick or the USB port (done it before…) but the built-in SD-card reader on the laptop allows me to have the SD card in the reader all the time without worrying to destroy it.