I've used this tool countless times over the years. It's a great little script for finding a point between two colours or simply looking at two colours side by side to see if they 'work'
The Colour Blender is licensed under a Creative Commons Attribution-ShareAlike 1.0 License.
Note - This page will not currently validate at W3C I've included it now to prevent delays in making it available and will amend to pass XHTML validation shortly.