Cubulus: Open Source OLAP ++
Cubulus is a new kid on the open source OLAP block.
Written in ~ 3K lines of python, it implements mySQL-based ROLAP w/calculated aggregations stored in memcached, and includes rudimentary MDX and distributed parallel query support.
It sounds like an ambitious project ... and one I'll definitely be keeping an eye on.
also on John's Open Source OLAP radar:
- Pentaho's Mondrian -- the original java-based ROLAP engine
- OpenI - kitchen sink platform similar to pentaho
- OpenOLAP - Big in Japan ( needs help on translation )
- Palo - MOLAP store for excel et al.
- LucidDB - trendy column oriented architecture
- MonetDB - also column oriented.
Note that I have only very limited experience with the above items ... my clients always seem to have a licensed copy of SQL Server around, which gives them free (zero-marginal-cost) analytics.