Perst is a fast, native Java and .NET embedded database, with small RAM and storage demands (includes Android, WP7 and Java ME support). eXtremeDB is McObject’s ultra-fast, small footprint in-memory database system (IMDS) for real-time applications.
eXtremeDB in-memory database.(Link) Product family includes In-Memory Database System, Cluster, Fusion, 64-bit, Transaction Logging, High Availability and Kernel Mode editions.
Download the Perst for Silverlight demo.Get full demo source or an in-depth article explaining the code. Launch the live demo application in your Web browser. (Link)