I would start with FBO.Gov. Look at the current solicitations to see what is open for bid. Look at the interested vendors, you may find subcontracting opportunities with them. Not all register as interested vendors so don't think they are the only ones biding. Look at the scope of the project and contact companies that specialize in that type of work. Look at recent contract awards and contact the winner for possible subcontracting opportunities. I have been involved with the chamber of commerce for a couple years and that has led to a couple partnering/subcontracting opportunities.

For Washington, DC construction contracts, you should go to the DC Procurement Opportunities Page at http://app.ocp.dc.gov/RUI/information/scf/indexopps33.asp and in the first box drill down to construction category of 9120000 and you will get all pending construction RFPs and bids. Jos A. Rivera, JD Rivera, Sierra & Company, Inc.