EDIT: Oh, yes, SilkRoad is probably bigger. But at the moment it's underground. I hate to qualify my statement, but I will anyhow. BitMit is the biggest, closest-thing-to-a-white-market that BitCoin has.
bitcoinstore.com has sold over $288,000 worth of stuff so far and it hasn't even been out that long. Unless you can provide some form of documentation that BitMit sells more than that, I'm gonna have to go with the idea that bitcoinstore.com is "bigger" than bitmit. So it's not just Silk Road that's "bigger."