Earlier this month, I stumbled upon a feature that Flickr was working on, and wrote about my experience here on this blog. It disappeared shortly after making its appearance, and showed signs that it was still a work in progress (and an impressive one at that). Now it's official. Flickr just rolled out their geotagging components today, and they are wicked impressive.
Start by using the Organizer and selecting the Map tab. You're then presented with a Yahoo! Local Maps Beta-like interface (say that fast three times) on which you can drag and drop your photos to geotag them to your heart's content.
From what I've seen so far, it's pretty slick. They have some interface quirks to work out, to be sure, but I'm sure that we'll see those ironed out in due course. It will be interesting to see how the Flickr community uses these features. I know that geotagging has been around for a while, but in my opinion, it hasn't been available to such a large community with such a compelling interface.
I haven't explored as in depth as Thomas Hawk, so follow the link for his thorough review.
Update: For those of you who geotag your photos using another tool (or just have a really fancy camera), Rev Dan Catt pointed out that Flickr can read GPS information found in a photo's EXIF data when a photo is uploaded. You just need to turn it on.
Update 2: Flickr posted their own very informative post here.
Update 3: Flickr users have geotagged just over 1.2 million photos in just 24 hours!