I am working on a framework/concept called ghostream (https://ghostream.com / https://github.com/ghostream/ghostream)
ghostream is a stream processing framework, built in C++ - it is a data stream processing framework. Having used numerous commercial ones (most notably IBM's Streams), and building various other part-frameworks (i.e. for time and budget reasons focussed on one particular thing) I has an itch to build an open source one (while storm and samza are definitely related, I feel they fall into a slightly different category - I'm all about the streams :) )
It is still in very active development - but the base is solidified now and the new test framework is starting to shape up nicely. There are a whole list of issues on github + a roadmap waiting to be exploited.
I have already started dog-fooding it in my other personal projects - the most visual of which can be seen here: http://jamielewis.me.uk/posts/2013-11-03-Mapping-Earthquakes...
If this strikes your interest give me a shout: jamie@ghostream.com.