This is my first addon for Firefox so it's really simple and a way for me to get my foot in the door. It adds a Mibbit! option in the tools menu that opens up a basic window to Mibbit that allows you to connect to the Mibbit IRC client while browsing. I will eventually add cool buttons and customizations, but what fun is a final release without some alpha/beta.
I hope you find some use for it as I know I will.
***NOTE: Mibbit has a info popup that you may have to accept about the URL but after clicking it everything should work fine.