rrd-merge merges RRD (round robin database) files together, including the files used by Ganglia, Cacti, and other rrdtool-based software.
statsd-c is a reimplementation of Etsy's famous/infamous "statsd" in C.
statsd-go is a reimplementation of statsd in Go (forked from gographite) with Ganglia submission support.
rrd-fixpeaks removes errant "peaks" in RRD data. It requires rrdtool.
A user-friendly, Web-based accounting system.
A high performance ORM for Java.