Last weekend I wrote a small collectd plugin for monitoring Redis and put it on GitHub: http://github.com/powdahound/redis-collectd-plugin.
If you haven’t heard of Redis before, it’s a key-value store similar to memcached with support for more complex data types like lists, sets, and hashes. collectd is a stats collection daemon which recently added support for plugins written in Python. This is great because there’s no way I’d write a plugin in C! Anyway, you can use this plugin to collect data about your Redis server like number of active connections, database size, commands processed per second, and memory usage. You can then use a tool like drraw to generate nice graphs:
More info and installation instructions on the GitHub page.