As another commentator mentioned, http://orientDB.com/ looks interesting as well.

Those complaining about Titan being abandoned, don't worry. Getting better graph features into the Cassandra family is one of the best things they could do. So consider this a win-win.

For those looking for a javascript variant, check out my project http://gunDB.io/ which is a browser based graph database. Definitely not as "academic" leaning as Titan, but it is more friendly towards web developers which Titan is not.