At Campaign Donors : Fundrace 2008, one can use a search tool to look up campaign donors by zip code, city, last name, occupation, or employer.
I came across the site by accident while doing a search on a company name. The site revealed that the president of the company had made a campaign contribution to George W. Bush in 2004. I tried a search on my zip code and the site returned a list of people in my zip code who had made contributions to either the Democratic or Republican party and the amount donated.
The site states the following:
All calculations are based on public records filed with the FEC of contributions by all individuals totaling more than $200 (and some totaling less than $200) to a single Republican or Democratic presidential campaign or national committee for the 2004 and 2008 election cycles.