Memcached, or other module(s), for low RAM system

I'm using a VPS with 1G of RAM. This is for sites that I host for other people that generally have low demands.

In an effort to squeeze out all of the RAM that I can, I've been toying with whether to use memcached, or maybe one of the other Apache modules. But I'm not 100% clear on how they work.

I've read the documentation, and installed memcached, but free -m and top -c didn't show any memory improvements at all (in fact, they were a little worse). But I don't know if this is one of those things where it looks bad on paper but the benchmark speed is faster, or maybe I just didn't configure it properly.

Can you guys advise me on whether memcached is generally a good option for a VPS like this? If not, any other suggestions for modules that I might consider?