I love RRDtool. It's fantabulous. But it is a pain to build and install. Here are notes for CentOS 5 (or red hat 5, probably)
Packages you probably need (in addition to "normal" packages needed for development):
yum install libpng-devel freetype freetype-devel libart_lgpl-devel
Once you have these, it should be a pretty smooth configure/make/install.
