A new script introduced in Ubuntu 9.10 Karmic Koala to add apt repositories and import the gpg key is “add-apt-repository“.
Sample usage:
~$ sudo add-apt-repository ppa:gmpc-trunk/mpd-trunk
For some reason there is no script to remove repositories that have been set up this way.
Luckily the guys from sourceslist.eu (it) wrote a script fixing this issue.
It can be downloaded either as a bash script or as deb package.
After the installation the usage is straighjt forward using the same syntax:
~$ sudo remove-apt-repository gmpc-trunk/mpd-trunk

Hello! I am the author of the script and the webmaster of the site http://www.sourceslist.eu. You should make a small correction to your article.
The correct syntax to remove the repository is “sudo remove-apt-repository gmpc-trunk/mpd-trunk” and not “sudo remove-apt-repository ppa:gmpc-trunk/mpd-trunk.
However on my site are totally alone, every collaboration is always welcome. Bye Ingalex
fixed. thanks!
remove-apt-repository ubuntu-mozilla-daily/ppa
unsuccessful removing – ppa launchpad repository not present or wrong syntax
You can use synaptic to remove repositories in settings->repositories. Or am I missing something?