I've been using MRTG for many years now to draw pretty graphs. It's a bit inflexible though and I'd written a kludgy script or two to graph things that wanted more than 2 lines, or that I wanted to dynamically configure. I'd been on the looking for something simple that would do this all for me and replace my MRTG + scripts setup. All of what I'd seen seemed a bit complicated to get up and running, and what I had was BALGE, so I hadn't really looked that hard.
At the start of the week, however, I got pointed at someone else's stats page, generated by Munin. The graphs were presented in a nice clear format rather than a million levels down a tree, and all the graphs for a host were on one page for at at-a-glance view. Of course there's a Debian package, so I thought I'd try it out. Very quickly I was up and running with my local machine being monitored. A little extra work and I had SNMP monitoring of my switch, allowing me to ditch MRTG. Slightly more work and I had my UPS being graphed too. Finally I installed snmpd on my wgt634u running OpenWRT and had that sorted too. Excellent. A lot less work than I expected and a much nicer setup than before. I'm sure there are other good options out there, but I found this one worked for me.
Oh, and while I was at it I discovered mbrowse, an SNMP MIB browser. I think I'd rather have something that showed me the values read from the device in tree form, but I still found it quite handy.