Why Tag Photos?
First off I should explain why you should tag your photos. Photo Tagging is the process of assigning a word or words to your pictures that help to describe the picture. Once tagged, flickr, zooomr, Picasa etc can group all of those related pictures together. It's a great way to organize and sort through a lot of pictures. For a good article on why you should tag photos and ideas on tag names see this article on digital-photo-secrets.
The tag data added to photos with iTag is embedded into the actual photo file using standard IPTC headers. By using the IPTC standard, your descriptions and tags are compatible in Zooomr, Flickr, Adobe Photoshop Elements, Picasa, Smugmug as well as many others. I use iTag to tag my photos before uploading to Zooomr or Flickr so that the tags on the pictures will be the same on my computer as they are on flickr.
Current Limitations of iTag:
Only works with jpeg files - it does not work with tiff, png, gif, raw or other photo file types.
Requires NET Framework 3.0
How To Use iTag
First, download and install iTag from here. If you don't already have the .NET Framework 3.0 installed, it will prompt you to download and install it first.
Once you've installed .NET 3.0 and iTag, you will get a "completed" confirmation. Click on Close and start the iTag program.
The iTag interface is pretty simple. There isn't a lot of help under help, but fortunately its pretty easy to use and navigate.
Select the "Open Images" button and a window with a file directory will open. Here, you select the drives where the pictures you want to tag are located. Select the files with your mouse or drag and drop photos from windows explorer into iTag.
Once you've added the files to the iTag interface, it will show those photos in the main window of the application. You can view these thumbnails using small, medium and large sizes.
To add tags simply type in one tag at a time in the "add tag" box and click add tag or hit your enter key. you can select multiple photos by using the control key. Once you have a decent set of tags in the tag box (lower left of the interface) you can just select the photo or photos you want to tag and click on the appropriate tags. You can also add a title and description for each photo.
Once you are finished tagging, select the save button and you are done. Your photos are now tagged and those tags will follow your photos into any application that uses the standard IPTC headers. [If you are uploading the photos to Flickr or Zooomr, do not resize when uploading the photos or the upload will over-write the tag info.] CORRECTION: You can resize when uploading photos to flickr or zooomr without losing the tags. I just tested this out and it worked fine. Thanks to ale for pointing that out!
Don't forget that iTag will also tag geodata in your photo also. This can be useful if you want to use your photos in Google Earth for instance. To Geocode photos, you simply drag and drop Google Earth place marks (*.kml, *.kmz) onto the selected photos. An even faster way is to simply copy a place mark to the clipboard, which iTag can detect. When geocoding, the data can also be saved as IPTC tags, to the EXIF fields, or both. Photos geocoded with WWMX Location Stamper are also recognised and can be viewed in Google Earth. Groups of photos can be selected and viewed in Google Earth. There is also an option to convert GPX tracklogs to Google Earth format.
iTag is a great application if you take any digital photos. I highly recommend it. To download and read more about iTag, go to the website: http://www.itagsoftware.com/index.php
Side Note: If you do use Adobe Photoshop Elements, please note that you can also tag photos in that application also. You just have to remember to "write the tags to file" after tagging in PSE so it will store that information in the file itself and be compatible in other applications such as flickr and zooomr.