All you have to do is go here and click on the link that says “Oh No Robot” (while in Firefox, of course). A box will popup. Click ‘OK’, and the plugin is installed! Then, just select ‘Oh No Robot’ from the search dropdown (top-right corner of Firefox), put in a search term, and TA-DA! You can now search Oh No Robot without having to visit the site!
And don’t worry, the plugin is T Campbell approved.