Metadata Deluxe Wiki - Embedded Metadata Subcommittee of the Visual Resources Association Data Standards Committee
International Press Telecommunications Council (IPTC) Photo Metadata
Flickr blog on EXIF, IPTC IIM, and XMP
Flickr Uploadr - Flickr's app for uploading images from a hard drive
Flickr Metadata Synchr - independent app for synchronizing images and metadata between Flickr image sets and a hard drive
IrfanView plus plug-in - software for adjusting photos that allows editing of IPTC (for windows), has capabilities for many file types, including jpg 2000 and many raw files (Windows)
Nikon Transfer - includes provision for creating and applying IPTC/XMP templates while importing images from a camera or other source.
Nikon View NX - software for adjusting photos that allows editing of IPTC and enables geotagging of images with Google maps, includes capability for standard file types and Nikon raw files
ExifTool - Reads, exports, and writes embedded metadata. It writes with commnand line prompts. Does a thorough job. Perl for Mac and Windows. Exe file available for Windows.
ExifToolGui - Graphic User Interface for ExifTool that enables editing of IPTC and Exif fields without using a command line. (Windows)
Exif Viewer - Firefox add-on that reads xmp, including custom panels, in jpeg images onlinle or on a hard drive (to use, select an image, then access the application through the shortcut menu). Results nicely laid out. Doesn't read as many images as EifTool, but it reads most jpgs.
FxIF - Firefox add-on that provides basic EXIF and the IPTC fields dc:creator, dc:desription, dc:rights, and photoshop:Headline (to use, select an image then view the properties in the shortcut menu. note: the FxIF title label is the IPTC headline, not dc:title)
Opera - Browser that displays EXIF information and the IPTC fields dc:creator, dc:description, and dc:rights (to use, select an image then view the properties in the shortcut menu)