Debasish Ghosh integrates Akka, a Scala implementation of the ☞ actor model, with Redis PUB/SUB support:

Redis (the version on the trunk) offers publish/subscribe based messaging. This is quite a big feature compared to the typical data structure oriented services that it had been offering so far. This also opens up lots of possibilities to use Redis as a messaging engine of a different kind.

via: http://debasishg.blogspot.com/2010/04/pubsub-with-redis-and-akka-actors.html

The latest version of MongoDB has introduced support for geospatial indexing. Joroen’s (@jvwilge) post is a quick guide to geospatial indexing in MongoDB based on a classical problem:

I recently finished my bachelor thesis about collecting gps points and discovering running routes from those points. The main bottleneck in my application was counting the number of points within a certain radius of a point. You basically have to check all the points to see whether they’re inside the radius. Let’s say you have 10^6 points (and I have), then (10^6)*(10^6) steps are needed. I advised to use a geospatial index with PostGIS in my conclusion, but that’s not really new and cool, so let’s give it a shot with MongoDB.

via: http://blog.xebia.com/2010/03/28/mongodb-geospatial-index/