Here is search logs of 650,000 AOL users. It's very interesting to view search history of particular person and analyze his personality. Let's do it together! Read more about AOL search database scandal or view research papers on web searching.
hsqldb.org
RDBMS with JDBC interface, client-server version, query tool, grid, tree, performance test class, servlet, and self-test program. Also supports pure in memory databases. [Open Source, BSD-like]