For Palm OS 5 see Uninstall Manager

Uninstall Hack will make sure that newly installed applications will be completely removed when they are no longer needed.

When you launch applications, from the built-in memory or the Expansion Card, they save data onto your device. This data is used by the application when active, and normally, will be deleted when you delete the application itself.
Each and every application on your device has to have a unique Creator ID which has to be registered with Palm.
Applications, in general, use their Creator ID to tag the data they save (files, preferences and various settings) on your device.
When you choose to delete an application, the system knows which files and preferences it needs to delete by comparing them to the application's Creator ID.
However, some applications (intentionally or due to a programming error) save items under a different Creator ID than their own; these items will remain on your device, occupying your precious handheld memory for good.
When using Uninstall Hack to remove applications, they will be completely deleted, including items saved under a different Creator ID.