I currently have a Nexus S with Gingerbread. I'm planning to travel oversea and I want to disconnect my phone from my cell phone provider but still be able to use the Nexus for wireless access at airports or hotels. Is there a way to achieve that in the OS without having to remove the SIM card?
The easiest solution is to simply use airplane mode. The wifi chip still works but the cell radio will be turned off, so you have no voice, SMS or cellular data capabilities. This will be in your settings somewhere, probably
Some phones also allow you to toggle airplane mode from the power menu, but I don't know if this is a standard feature of the Android OS.