Including these as part of an emergency procedures binder (maybe even a wiki!) could be a very valuable and easy way to provide information to colleagues at other institutions who are often eager to help you after disaster strikes.
I haven't forgotten about the use of Flickr for sharing photos in the wake of a disaster, and you may have heard about how a photo on Twitter broke the news about the plane crash in the Hudson River last month. I'm not currently aware of anyone writing up these or other social networking & media methods up as part of emergency preparedness plans, but think they've certainly shown a high return on very little investment and should be considered.
2/27 edit: Apparently I was picking up the Twitter/social media emergency communication vibes from the Seattle Times while I was writing this, check out the suggestion from a King County council member below in response to some bus service meltdowns due to snow in Seattle yesterday
"Given the increasing sophistication of modern phones and wireless Internet providers, I encourage Metro to take immediate action to use instant messaging, Twitter, neighborhood blogs, and customer self-reporting systems to keep Metro operators and riders connected," Constantine said in a statement.
He said inexpensive ways exist to reach riders. "It doesn't seem like they've got people who are savvy at that."