I want to make a new contrib development based on NoSQL databases like Cassandra.
Does anyone know of a University or Research Group, or anyone else, who works in "Geo-Cassandra" currently?
There's a number of people interested in the GeoCouch project for CouchDB, and MongoDB's geospatial indexing. Truth be told, though, PostGIS in the traditional relational world captures most of the attention, and has a very large feature count by comparison. These slides are old, but might be helpful. I've seen Cassandra discussed primarily in the context of being a potential container for geohash indices.
There's a video you should watch by SimpleGeo describing the creation of a cloud geospatial platform on Cassandra called 'Storage', but they appear to have completely ceased operations. There might be some useful things in their Github, but I don't think they open-sourced their main product.
Regarding interesting GIS computational tasks: It seems to me that most geospatial operations are trivially parallelizable, but scant accessible software exists to push them through OpenCL/CUDA, a private grid, or cloud services. As a GIS user, I'd like to run a low-priority background task (we'll call it Geo@Home), which keeps my CPU/GPU saturated with the office pool's queued geospatial tasks, and then allows me to submit tasks which are transparently distributed to the grid and returned to me. I've read of MRGeo, a Hadoop map-reduce geospatial framework that planned to open source, but that appears to have disappeared when GeoEye absorbed SPADAC.
I can't help you on academic contacts in this area, except to note that the GIS section of a university Geography department and the database section of a university CS department are often completely disassociated, and interested in different things. If you're just looking for professors interested in furthering GIS development, you might look to the proceedings of recent conferences for university affiliations.
SimpleGeo (when they existed) did a presentation at the SF GeoMeetup about Bringing Geo to Cassandra. Here are the slides he used.