Flickr has added an easy way to geotag photos - it's just a case of drag and drop. The map is a little coarse, and so it can be hard to get exact spots, but it's not bad at all.
This is discussed on FlickrBlog
I've started to map my photos - but don't intend to do them all (is it better to have a position which is innaccurate, or no position at all? I think the latter.)