Sean, you bring up a useful point about intellectual property rights here. I have been wondering about this myself. My contract - which I picked up from another grant writer/consultant - states that I maintain the copyright to the material I produce. The agency is entitled to limited usage rights. The arrangement is similar to that of a photographer's work (unless it's work for hire). So far it's only come up once with a client, and at their request I adjusted the contract by changing the terms slightly and adjusting the rate.
I'm curious about what contract language other people use.