I was reading the description of the Email Paste extension for firefox and it gave me an idea for another extension. Sometimes you want don't want to give out your email for a site, but it involves enough personalization that you don't want to use bugmenot.
I'd like to be able to see that they want me to register, click a thingy, a prompt pops up for a master password and I have a random mailinator(or other) account generated based on the domain, pasted in, and a password based on that site's domain generated. A tab opens up in mailinator to click the confirmation email.
When I go back to the site from a new browser, or after losing my saved passwords, it autogenerates the same user/pass based on the domain and my master password.
This could be done from an extension or a bookmarklet. It could also be done with a greasemonkey script. However, it would need to be turned on for http(s)://* and I think adding tons of GM scripts for * ends up slowing down your browser.
Also, maybe you want to just have a junk email account and always use that. Shouldn't be tough to also allow that.
If anyone likes this idea, I'll get to work on it.