Shoutbox

Download Quick Contacts Adder script.

Then use the command:
/addcontact email@domain.com,email2@domain2.com

That will bring up multiple boxes to add contacts, which is easier than clicking add, over and over again.

However, typing too many in one command may make your computer crash or something, so you may have to limit it to a certain amount. I don't recommend doing it with all of them at once!

Edit: I managed to add 100 contacts at once, took a minute to load all the boxes though After that you just click 'Save' 100 times Easiest way I know of!

Screenshot: