The man who comes back through the Door in the Wall will never be quite the same as the man who went out.
Wildhoney mentioned using Prototype to cut down on the amount of code that you have to write. Remember that you can compress Prototype down as well, and if you're using more modular libraries/frameworks (Mootools is a good example) then it really makes sense to only ever include the parts of the libraries/frameworks that you're going to be using (if that's possible).
Other popular compression tools include YUI Compressor, Douglas Crockford's JSMin and Dojo ShrinkSafe. I don't know if any of those have a web interface to copy/paste code from/into.