1. Neo4j
2. Google Pregel
   1. http://googleresearch.blogspot.com/2009/06/large-scale-graph-computing-at-google.html
3. Twitter's Flock DB
   1. No graph traversal
4. AllegroGraph
   1. Lisp
   2. http://www.franz.com/agraph/allegrograph/
   3. Hardcore enterprise
      1. Kodak
      2. Ford
      3. Pfizer
      4. Nasa
      5. DoD
5. GraphDB
   1. .NET
   2. Microsoft Azure
6. InfiniteGraph
   1. http://www.infinitegraph.com/
   2. CIA used
7. OrientDB
   1. http://www.orientechnologies.com/
8. InfoGrid
   1. http://infogrid.org/
9. HypergraphDB
   1. http://www.hypergraphdb.org/
10. Ravel
    1. Open source version of Pregel
    2. http://www.raveldata.com/
11. Microsoft Project Trinity
    1. http://www.readwriteweb.com/cloud/2011/03/microsoft-research-watch-ai-nosql-big-data.php