A handy site for those who have a computer to hand before they start their journey: a map overlay from the BBC which shows reported weather plus traffic and rail (including underground) incidents, holdups, etc.
Find it at http://bbc.blueghost.co.uk/site4.php# (yes, we do mean the # - don't ask us why it's there).
It's YAGMM - Yet Another Google Maps Mashup. (Maybe we'll start calling them Yegomamas..). Certainly very neat, and another project to emerge from the BBC Backstage concepts melting pot.
(Thanks for the link to the Map and GIS News Blog, which is itself a very useful resource for anyone interested in maps or mashups, but particularly both.)