The wealth of packages available to Ubuntu users is vast, and can often be overwhelming. I suggest that the Add/Remove tool be able to recommend packages which are not already installed, based on the user's unique setup and activities.
For example, a user with a lot of music files can have Audacity recommended. Users with a webcam can have Cheese recommended. Users with a HP printer can have the HP printing utilities recommended. Users with raw digital photos can have UFRaw recommended, etc.
These recommendations would appear in the Add/Remove application the next time it is run (perhaps read from a file, written to by Nautilus and HAL/DeviceKit when they encounter new files and hardware). The user should be able to refuse a recommendation and never have it appear again, to prevent the list becoming unmanageable.