redis also supports consistent hashing in many of its drivers (including the Ruby one). It also supports a nifty way to only use part of the key as the consistent hashing key so that you can ensure certain data is stored on the same server. For example, if you use the key "mydata-{123}" only the "123" part will be used by the consistent hashing algorithm. Of course, Riak is also a good example of consistent hashing.