|Computer Janitor on Ubuntu 11.04|
Ubuntu comes with a handy little tool called Computer Janitor designed to help you find and remove obsolete software packages. It doesn't matter how tightly we control the packages that get installed on our computers, obsolete or orphaned packages inevitably accumulate over time.
In particular, this happens when we perform system upgrades from one version of Ubuntu to another. Old versions of packages are left over when newer versions of software that depend on them stop using them. Or, uninstalled software may have their dependencies left installed when they should be removed together. Thins like this happens. Software isn't perfect, after all.
If you use Update Manager to upgrade your Ubuntu then this problem is minimised since Update Manager will automatically perform some cruft cleanup activities as part of the upgrade task. Even so, new versions of Ubuntu come once every six months. That's six months for you to accumulate cruft in your system as you try out various software and remove them when you find you don't like/need them anymore.
Computer Janitor can't get much simpler. Uninspiring UI aside, the tool is actually very simple to use. Just check the items it finds that you want removed (usually they're all already checked for you) and click on the only button there is. Computer Janitor will do its thing and those obsolete packages should get removed from the system. That's more space for your data and less occupied by cruft.