I got a Crumpler Pretty Boy for free which is quite well proportioned. The camera and lense fit nicely and it should be able to hold a speedlight and another lense without much trouble. There's also plenty of pockets for remotes and filters and the like.

Which brings me to another question, is it worth spending 50-odd quid on a Hoya or Sigma polarising filter from Jessops, or are the cheaper ones from far east on ebay worth a punt?