memory usage log/graph?

Does anyone know of an easy way to track memory usage over time, just like CPU and bandwidth usage? I mean, something that'll let me know how much memory/swap I was using at the time of a surge in web traffic while I was sleeping.

I could probably do something like free -M >> logfile.log every few minutes using cron, and then write another script to analyze the resulting logfile. But there's got to be a more elegant solution than that! And I don't want to be staring at htop all the time.

Thx,