It's an extremely short notice, but we're going to have the first meeting tomorrow, that is - Saturday (2009-04-04) 14:00, in cafe on top of the Waterstones bookstore near the Piccadilly Circuis Tube station.
If you want to know more, email me (Tomasz.Wegrzanowski@gmail.com) for details. Or just come straight away.
Hopefully we can get it going, and the second meeting with be better organized.
That's what we'll do, there's no widely recognizable "rationalist" symbol, so we can use words for it.
A balance (decision theory) and an urn containing colored balls, with a few balls drawn (Bayesian inference).