Double At is a new jailbreak tweak that is dead simple but extremely useful. If you're tired of entering your e-mail address for everything and you're jailbroken, you may want to give Double At a try.
You can define your e-mail address within Double At and when you need to enter it into a form, double tap the "@" symbol on your keyboard and it automagically inserts your e-mail address into the field.
It's simple but definitely helps if you're the type of person that either constantly has to fill in forms with your e-mail or send your e-mail address to people via Twitter, e-mail, or whatever means you find necessary. Hit the link below to check it out!