So the first thing to do is add the repository in question. For example, I added deb http://ppa.launchpad.net/compiz/ubuntu jaunty main, but after refreshing I got an error that read, "W: GPG error: http://ppa.launchpad.net jaunty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2ED6BB6042C24D89"
To fix this all we need to do is run the following command from the console:
gpg --keyserver hkp://subkeys.pgp.net --recv-keys 2ED6BB6042C24D89
gpg --export --armor 2ED6BB6042C24D89 | sudo apt-key add -
All that one needs to do is replace 2ED6BB6042C24D89 with the key listed in the error and you are back in business.
If anyone happens to know of a better way, I am all ears.