Lately I've been very busy with work, but I find that I still need to keep an eye on the Linux servers I have kicking around at home and at the office. I use Nagios for basic monitoring (ping, smtp, http) but wanted something a bit more fine grained on the actual host itself. I stumbled on munin when doing some Google searching.
Munin's homepage is here: http://munin-monitoring.org and I'm running it on a variety of servers at them moment (mostly Ubuntu and Debian). It supports quite a few distributions and operating systems so check it out if you're interested in seeing what's happening on your servers.
I like the many graphs that it produces to demonstrate what's happening and I also fell into the trap of trying to over-configure things. There are only a couple of basic things to change to suit yourself, restart apache2 and munin-node and it's slamming. It also monitors multiple machines - install munin-node instead of munin and munin-node and configure as recommended. I thought I'd be tricky with it and things didn't go as planned so it appeared that it wasn't working. I was over thinking it though and it did work, very well actually, once I found the spot it was creating the files in :-)
A handy app and a nice way to keep on top of your servers!