It depends on what info you want that was on the phone. Contacts, Mail, Calenders, pics, music, notes, apps etc can all be set to sync through iTunes and all will be available on the computer you sync the phone with (assuming it's a Mac, not sure about Windows as I don't use it with my phone). If you synced them with iTunes, your info is there.
As for syncing from the phone itself, you can sync most of the above remotely if you have Apple MobileMe service and syncing setup. It won't sync apps though. It will sync calenders and contacts mainly, along with some e-mail. Also, with MobileMe you can locate your phone if it's turned on (Geographic position displayed on a map) and you can remotely wipe your phone so whoever took it can't get your data.