AudioShell
There's no easy way to add ID3 tags to audio files flying below the radar of the CD database services. Tag editors simplify the process but all of them come up lacking in some way. AudioShell lacks the capacity to batch edit ID3 tags, but it really doesn't need to. After installation, right click virtually any audio or video file and quickly edit the files properties without the overhead of an additional app slowing down your system. AudioShell is the best app I've found for adding Album Art to a file. The shell interface provides a quick snapshot of media file properties and a neatly organized interface for making changes. If you record and tag your own audio this is a perfect addition to your suite of media tools.