Tailor is a tool to migrate or replicate changesets between ArX, Bazaar, Bazaar-NG, CVS, Codeville, Darcs, Git, Mercurial, Monotone, Subversion and Tla repositories.
« Solr is the popular, blazing fast open source enterprise search platform from the Apache Lucene project. Its major features include powerful full-text search, hit highlighting, faceted search, dynamic clustering, database integration, rich document (e.g., Word, PDF) handling, and geospatial search. Solr is highly scalable, providing distributed search and index replication, [...] »
Prophet is a new kind of database that offers peer-to-peer opportunistic replication (it's basically like a database version of the Sync framework). It's a very lightweight semi-relational database.
SD (Simple Defects) is a bug tracking tool based on Prophet that is not-only peer-to-peer, but it syncs with other bug tracking tools!