Was it Tradehill?
TradeHill provided its users a hosted (shared) EWallet. That means the user account is assigned an address from the wallet, but the wallet is owned and managed by the EWallet provider.
Bitcoin is a pseudonymous digital which can be used anonymously. In this instance, those funds were transferred and spent long ago.
You can try to contact TradeHill to see if you have (had) an account with a balance yet.