There is a weekly magazine called Time Out - but i don't know if it puts all club listings on to its website, only its print copy.
But some good club websites to check are:
www.the-end.co.uk
www.turnmills.co.uk
www.fabric-london.com
www.the-cross.co.uk
Also, there is www.harderfaster.com, or is it www.harderfaster.net - although that really only does hard dance type events, but it does give a good overview. I think you can even "join" like biggie and post on their bulletin boards, go to meet-ups, etc. Tho i don't really know, cos i don't follow the hard dance scene too much anymore - too much of a house boy now
www.sorted.org/london can also be helpful