Canadians: if you have relatives visiting England and are concerned about them, Foreign Affairs has a hotline set up: (Have their full name, birthdate, and passport number ready) 1-800-387-3124. Other countries also have hotlines, see the community above.
The CBC's coverage seems to be quite good, although I'm not having any trouble reaching the BBC's site, which is comprehensive and likely to be much more useful for people in the UK and needing information.
If you are in another part of the world and are willing to contact local friends and relatives of people who are in England, sign up here -- please check to see if anyone else in your area has already volunteered.
Time for me to get some lunch and do some work...