Paste and Go
This extension emulates the "Paste and Go" functionality found in Google Chrome when right-clicking the address bar, for all of the input text boxes on websites.
The extension works by trying to find the closest <form> (traversing upwards) to the input box in which you want to paste, and submits it. If no <form> is found, it then tries to search for the closest button and click that one.
After installing the extension, don't forget to refresh the tabs that you currently have open if you want to use it in those pages.
The source code can be found at https://github.com/dreasgrech/PasteAndGo
More information and technical details in my blog post: http://blog.dreasgrech.com/2012/01/paste-and-go-google-chrome-extension.html