Thanks everyone, especially dundee and doctor_torrse.
Just to clarify: Expedia works through Terrapass, which was founded by Dr. Karl Ulrich at the University of Pennsylvania in 2004. According to their website, "All TerraPass projects are verified by an independent accredited organization according to a published offset standard. All verifications include site visits, audits of the project data and project monitoring equipment and practices relative to the standard used."
It then notes, "Every project is conducted and verified according to one of the following appropriate standards: Voluntary Carbon Standard 2007, Green-e Climate, Chicago Climate Exchange Offset Protocols, California Climate Action Registry, EPA Climate Leaders, ISO 14064-2, and Gold Standard. TerraPass publishes the standard to be used for each project on our website when we solicit comments for new projects, and in our annual project portfolio. Every 2008 TerraPass will be fulfilled with verified emission reductions from vintage year 2008; these projects must have started operating no earlier than January 1, 2002. As we consider new projects, we publish the project name and location on our web site and invite public comments."
You can then click on their portfolio (here's the link from 2006) to see how many offsets they purchased and how much carbon they took out of the air.
http://www.terrapass.com/projects/portfolio.htmlWhat is missing is how much money they took in and whether or not all of that money has gone into offsetting and basic admin, but it is one of the better sites I've seen in terms of transparency.
I guess what is driving this right now is that I cannot ask faculty NOT to travel for research (although I could encourage regional conferences). In other words, I cannot force them to pollute less. What I can do NOW and with minimal expense is offset their travel carbon emissions.