The BBC News report is very clear. The audio quality on the Sky News report is less so, and there are interesting comments on the Gaurdian's blog - one of their reporters was arrested.
The Foreign Office's advice to travellers advises caution, but that is normal. They have not upgraded the risks of travel in Egypt.
[Later] All Football matches this weekend have been cancelled. The leader of the opposition has arrived in Cairo and will partake in demonstrations tommorrow. Today's demonstrations included Giza (near the station, not near the pyramids). I'll provide new news links tomorrow.