One of our customers has posted an interesting article on his blog, Making the most out of a 64MB VPS. He explains a few of the difficulties that can be encountered in a limited memory environment, shows how to decrease your memory usage, view performance statistics, and more... My biggest suggestion, personally, however... if you're going for an account with only 64 or 96MB of ram, you will see performance advantages from going with a 32-bit OS. The only reason we don't make it default, is that a mix-arch Xen installation was sort of experimental until very recently.