iTag Build 190

iTag is a free tool that adds title, description and keyword tags to your jpg photos.
The captions you enter are embedded into each jpg file using industry standard IPTC and XMP headers - all in a loseless operation that doesnt degrade the jpeg image.
Many other applications understand IPTC/XMP too - so once you have annotated your photos with iTag,
any IPTC/XMP aware application will automatically fill out the title, description and tag fields where appropriate.

If you already have a number of tagged photos, build an index with iTag so that you can search for your photos like this.
If you do all of your tagging in iTag, the index will automatically keep itself up to date.
(Search functions in Picasa, Copernic and Windows Vista will work with iTag edited photos too).

iTag can load geocoded photos into Google Earth like this.
Simple geocoding can be performed by using Google Earth placemarks. If you have a GPS you will want to use something like WWMX Location Stamper instead.

iTag comes highly recommended by Brent Evans, was given 5 stars by freewaregenius and has been featured on lifehacker.