Along the same lines of freeing up memory:

A couple days ago I tried changing the swappyness setting of the vm on a box that I have a few servers on:

echo 100 > /proc/sys/vm/swappiness

Suddenly, a ton of unused memory that my apps had been eating up was forced into swap and my apps have been way faster since then. Anyone had similar results? Would this be something that shared hosting providers with severe memory limitations should consider doing?

You can do > to get a greater-than sign. But be careful if you edit the post later, it reverts back; a known bug on the Feature Requests thread.