http://www.wiggle.co.uk/muc-off-water-soluble-degreaser-500ml-aerosol/

It's probably just strengthened white spirit in a can, but my god its brilliant, and its a huge can of it, so I think its pretty decent value. Really cleans up chains and cassettes so quickly, great fun to use on filthy bikes.
And its also amazing at cleaning your hands after working on the bike. Spray a bit on to one palm, rub hands together, rinse, and your hands are spotless.
Any others?

