if you had
- 4 software developers
- any open source software
- server hardware
- internet connection for hosting
- 100 person days in which to do it?
if you had
How about a site equivalent to Rent-a-Coder but for non-profits to solicit volunteer or low-cost developers for public service projects (i.e. make your question easy for the next guy in an equivalent situation). Given the current economic troubles, there are likely to be both a lot of unemployed developers and a lot of troubled non-profits (and a lot of demand for the various kinds of help those non-profits provide). Let's put them together.
Add a point system like StackOverflow so you can earn points by helping out non-profits with their web applications or whatever. Then go get some corporate sponsorship so that you can turn your points into credits at Amazon.com or some such.