Hello all, I am looking for a javascript development environment (free, open source would be nice too) that allows for tracking variables and their types, exceptions etc etc

break points would be super cool too.

Does something like this exist?

Also, what options for javascript interpreters are out there? Currently I have only ever dealt with the browser processors (IE's and Mozilla's) through the browser.

Install firefox on your development machine & install a plugin called firebug. It allows you to track variables,exceptions.
You can even set breakpoints too