The 'Marriage (same-sex couples) Bill' is being debated today. The vote will take place at 7pmGMT (2pmEST) and is expected to pass by a healthy majority.
The Bill will then pass to the House of Lords in due course where it is also expected to pass.
I'll update with the vote result as they are announced if someone else doesn't do it first.
Gay marriage is expected to be legal at some point in 2014 in England and Wales. Scotland is expected to legalise beforehand. Not sure where Northern Ireland stand, but more time likely needed for that region.