I'm looking for one place that summarizes the main properties of the NoSQL databases that I keep seeing referenced - in particular, MongoDB, Riak, Redis, Memcached, Membase, and Cassandra. Types of queries, acid, architecture for/properties of scaling, etc. All in memory, overflow to disk, backup on disk, or mainly only indexes in memory?
Probably one of the best source which summarizes basic information (and points you to more detailed source in the first place) about various nosql databases is this website. Other than that you should check out these: