MySQL Quota Daemon is a lightweight tool for limiting database sizes. As the MySQL server has no support for preventing disk from getting filled up, an external one is needed. Other solutions are often bloated or to obscure to use. This one keeps low profile, being both nice to the system it runs on and easy to use.
I commit to the coolest DVCS of them all. It integrates code versioning with bug tracking and wiki, all in a single repository file processed by a single executable file. Furthermore it's pretty easy to learn and has a very helpful user community. Seriously, if you're a programmer, check it.