Android - Can someone identify this icon (looks like a ear) in the notification bar?

It's supposed to represent a hearing aid, and it means that Hearing Aid Compatibility is enabled.

It should go away if you go into the call settings and disable the hearing aid option. It'll either be something like Settings->Calls or pressing the Menu button on the dialer to get into the call settings (I think it varies some).

Supporting source, second source

For the Galaxy S3, this indicates that the telecoil mode (aka T mode or electromagnetic coupling) is active. As eldarerathis mentions, this is a type of Hearing Aid Comparability. It involves using the speaker coil in a specific manner to inductively couple with a compatible hearing aid.

In this mode, the hearing aid shuts off its microphone and receives audio only from the phone, effectively eliminating background noise and giving better performance than just using the hearing aid to pick up and amplify the phone's normal audio (which is known as M mode or acoustic coupling).