Python disk-backed cache (Django-compatible). Faster than Redis and Memcached. Pure Python. Thread and multiprocess safe. SQLite database and directory on the file system.

Setting up an LVM cache on an SSD can supercharge LVM.

A fast NoSQL DB, that uses the same RESP protocol and capable to store terabytes of data, also it integrates with your mobile/web apps to add real-time features, soon you can use it as a document store cause it should become a multi-model db. Uses Redis' network protocol so it's a drop-in replacement. Has some helper functions built in. Aims to be easy to use, with minimal configuration.

Redis is another key-value datastore (a distributed hash table, if you like) that can be used for either caching of often used objects or a database to build applications on top of. Can handle just about any serializable data structure, from strings to sets. Clusterable - uses master/slave replication. Written in C but has bindings for any programming language you're likely to know.