Most of the lead providers, search the public information bases and resell what you can obtain at no charge.
Take a look at this example for public projects:
http://publicnoticeads.com/NJ/search/view.asp?T=PN&id=680\2192007_5863520.HTM
There are also sites for private construction bids.
The smaller jobs are usually sites that attract price shoppers, these may cost more to buy then they are worth.
