I came across Pawel Plaszczak blog post that describes a new product from JBoss named Infinispan (still in beta), which aims the data grid market (seems like things are getting warmer). Pawel also provided a deep comparison between Inifinspan and leading commercial products such as Oracle Coherence and Gigaspaces XAP.
This product is still in beta, and is missing features that exist in the commercial products, but it's worth to take a look on it,
Moshe Kaplan. RockeTier. The Performance Experts.