Does anyone know of a good website for finding out what scientific conferences are on? (I'm in a molecular biology type area if that helps) None of the posters around the building seem particularly relevant to what I'm doing, and I'd like to find out what's out there before I blow my funding on one that might turn out not to be the best.

Try www.conferencealerts.com

If they're the helpful type, supervisors/advisors should be good at finding you a good one, or even postdocs. I found all mine by word of mouth.

another good way to find out about conferences is to sign up to academic mailing lists in your field at www.jiscmail.ac.uk, this is where I get my information from.