iOS 5.0.1 was released today, for the first time you can update your iOS devices without having to sync them to a computer running iTunes.
To do an over the air (OTA) update:
1. On your iOS device running iOS5, go to Settings -> General
2. Select the new Software Update option
3. Tap Download and Install on the update details view. Unlike the usually 600+ MB iOS updates, 5.0.1 is only ~45 MB. The download should finish in a few minutes.
4. When the download completes, you'll receive an alert to complete the install. After your device restarts, that's it - you've now completed your OTA update!