Re: btw, collectd
Ah, sorry, didn't realize at once it's a perl project. Makes plugin-related suggestion sort of funny. :)
Did you see also collectd?
So far the only problem with it was behaviour in OpenVZ container (e.g. CPU usage would dance between something reasonable and plain 100% -- not sure it's not OVZ's UBC problem), but otherwise seems nice, lightweight and stable.
monitorix's public record on freshmeat starts a year earlier but still you might decide to look if some productive cooperation is possible, maybe on plugins?
Will give monitorix a spin, either way. :)
An open, cross-platform journaling program.
A scientific plotting package.