If you do want to try it... here is some info about setting up ubuntu to do it...http://ubuntuforums.org/showthread.php?t=395435
Reading some of that thread though, it more or less confirms what I was thinking... this isn't likely to increase your performance by much/at all.
* It's only going to make any difference if you're already using all of the 2GB RAM in your machine
* Your card is going to have to be faster than the hard disk for it to perform any better at swapping than your disk currently is
* It will trash your SDHC card eventually because they are not built for this sort of usage
* I guess it will use extra power so your battery wont last as long
So, I personally wouldn't recommend this...