[ghporter]

Having been woken up (so to speak) by reading about how pervasive and detailed EXIF data in pictures can be, I have realized that I want to be able to edit this data in my own digital pictures. What editors have our estimable membership used and which ones have you found to be good/bad/interesting?

[Cold Warrior]

I like Exif-o-matic for single or bulk exports to explore exif in images.
Exif-O-Matic @ Rahulbotics : export meta-data out of digital images

And PhotoGPSEditor for a more detailed look at images and an easy way to change gps info for one or more images.
PhotoGPSEditor - MMISoftware - Makers of software for Mac OS X, the iPhone and the iPod Touch

If you want to do a lot more, especially to examine exif alongside hex, or to rip out all exif headers into an interactive html document, then you need to use exiftool.
http://www.sno.phy.queensu.ca/~phil/exiftool/

[Cold Warrior]

Tips:

exiftool -h -w outputfilename inputfile
This writes the exif of inputfile to html format (-h) to a file (-w) instead of Terminal's window. Run without -h to output to a txt file.

exiftool -htmlDump -w outputfilename inputfile for an interactive html display as seen here.