This permission form is comprehensive and includes permission for online presentations in Blackboard Collaborate, blogging, wikis, google apps, podcasts, videos, social bookmarking and RSS as well as images. It is very comprehensive and useful. Again, I'm not a lawyer, but of the forms I've seen, I think this one is comprehensive.
Here's a google apps consent form for another district. It also references the Network Access Agreement (We call ours an AUP - or acceptable use form) which is an important practice that ensures students know they must use the network in accordance with guidelines already given.
Another website example of disclosures about the use of Google apps from a district in Oregon. This also references their Acceptable Use Policy (AUP) and frequently asked questions about Google Apps, another good thing to include.