iPhone 4 passcode lock disabled and no access to iTunes
You can quickly get going again by erasing the device and restoring from iTunes.

The backup doesn't need to be in iTunes, but if you don't have a backup, you may be starting over.

See http://support.apple.com/en-us/HT1212 for an up to date explanation from Apple as well as more details on the process for your computer or OS of choice.