What are some of the others? The last time I looked, MonetDB and LucidDB seemed to be the most popular column-store open source projects, but they seem to have been mostly subsumed by proprietary products.
Whisper (backend for graphite), cube, ganglia... possibly more. I used to build things directly on top of rrdtool, but the schema definition can be a pain when you've got a lot of dynamic data.