By quite a long margin: 25% more, in fact (Salesforce.com market cap: $7.5B, GM, just under $6B).
Other unlikely companies that are now worth more than GM: Ryan Air; Pitney Bowes; J C Penney; Autodesk; Bed Bath and Beyond. Even tech. train wreck, Sun Microsystems is worth 25% more. And in a case of a piece being worth more than the whole, automobile parts distributor, Genuine Parts Company, and dashboard GPS maker, Garmin, are each worth $500 million more than GM.
Use Google Finance to screen for companies worth more than GM.