Launchpad-Getkeys is a script (comes packaged in a .deb) that automatically imports all missing GPG keys, even if you're behind a firewall.

How do you know when you have a missing GPG key? Here's an example: when you run "sudo apt-get update", you'll see some errors like this:

[...]

Fetched 47.0kB in 6s (7,710B/s)

Reading package lists... Done

W: GPG error: http://ppa.launchpad.net maverick Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B2DFD25316B94077

W: GPG error: http://ppa.launchpad.net maverick Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 1FFD34C9EB13C954

W: GPG error: http://ppa.launchpad.net maverick Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EF4186FE247510BE