Apple released a minor update to iPhone software. The latest version is 2.2.1. You can download it via iTunes.
It fixes a bug (it was introduced in version 2.2) in photo software that caused blurry image when an image was saved from the mail application (MMS equivalent for iPhone). Another change is improved stability of iPhone Safari browser.
It is supposed to work with iPod Touch as well. If you are not sure, you can wait a day or two to hear about others' experiences before updating.