I'm a subcontractor, and I use this app to help keep track of my tax-adjusted income vs. expenses. Once you establish an "economic forecast" by filling in the 4 initial text input fields, you're able to add up individual expenses, .. drag and drop them to new positions (if necessary), .. and then delete each expense once it's been paid off. The result is a "tape roll" like summary of where you're at financially (meaning an estimate of how much extra spending money you should have left over if everything works out as planned).
Feel free to bookmark this link if you find it useful in any way, by the way. You'll see that it uses HTML5's local storage functions, and doesn't require any server-side scripting. In fact -- you can just save it down to your local machine and to run it from there if you prefer.
Thanks, -- and happy new year!