New camera models with GPS or GeoTagging as an embedded feature are becoming more and more common, or you can buy a GPS/GeoTag unit that hooks up to your specific camera. If you aren't in the market for a new camera, and don't have the loot to splash out on a tagging system, there are a few ways around it for the more casual geotagger.
How often have you returned from a trip, only to start going through your photos and not really knowing where half of them were even taken? Of course it's a no-brainer to identify the Eiffel Tower or Colosseum, but what about the umpteenth church or random street corner with the awesome balcony?
There are a number of inexpensive apps you can download to your iPhone or Android that will sync with your camera's clock, allowing you to use software to sync the information later when you download the pictures to your computer. But if you're already on the road or don't want to take your phone, there are a few hacks to help you keep track of things.
Not all of these will work in every situation, especially if you take a vast quantity of photos over numerous locations. It can still be time-consuming, but can hold you over or work in a pinch if an app or accessory tagger fails. If you have any tips of your own, feel free to suggest them in the comments. Happy tagging!