It's pretty much accepted that women are generally far better at this than us men. I found this article from a few months ago and it looks like it has indeed proven to be the case.
BBC News - Women 'better at multitasking' than men, study finds
I don't think I'm particularly good at it but because I can play the guitar and sing at the same time... people say that I am. I've always been a bit unsure what constitutes multitasking. Surely something as simple as talking and driving would count? Pretty much everyone is good at that.
What kind of tasks do you reckon constitute multitasking? Are you any good at it?