Kasie- I think that Virutal Field Trips can be a wonderful addition in the classroom. Here are some links to get your started.
- Check out the Smithsonian Musems - they have virtual tours - http://www.mnh.si.edu/panoramas/
A larger question is what is your goal of the virual field trip? Are you trying to find connections to standards? Are you trying to find resources that can be an extension to a particular topic? If you could share a bit more about your goals I imagine that there are other community members that may have ideas for you.