Hash Generator
The hash generator is useful for creating random strings. It is highly customizable as to which characters will be used in your string. It uses jQuery and the Check Box Group plugin to manage the checkboxes, although I can not remember where I downloaded it from. I imagine the jQuery plugin repository, but I'm not sure. The hash generator can also be used to create a salt for your passwords.
What is a salt? A salt is a random string that you add to the beginning or end (or both) of a string before running it through a hashing function such as md5 or sha1. Usually this is used on passwords, and is run to store the password, as well as when checking validity. Keep the salt secret and it will reduce the effectiveness of rainbow tables.