JavaCrypt
The form below will encrypt text using the algorithm of your choice (if your choice happens to be MD5). It does this using JavaScript. Why did I create my own? Because I want assurance (for myself, and for you if you trust me) that the text isn't being sent anywhere. There are many online hash calculators but I don't remember seeing any that stress this.
So, I have done what I can on my end to at least ensure that text entered in this form never travels over a network. The inputs are not part of an actual HTML form element, so it shouldn't be possible to accidently submit them. I also can verify that the JavaScript does not make use of HTTP request functions.
Input:Hash:
The md5 script is by Paul Johnston. I have edited it a bit — namely, I made it into a "class."
I plan to add more algorithms as I develop a need for them.