What online tagging sites are there?

Cool content, interesting use of geo-tagging.

For example, if today I read some theory about dynamic programming, then I want to be able to classify the problems on various competitive sites so that I can solve many problems related to it.

Google Maps and Google Earth both display placemarks of photos using embedded Lat and Long, but they don't appear to use embedded compass orientation metadata to indicate the direction the photo was taken.  I just saw the 360 Panorama iPhone App uses...

im just looking for a good site that is free to tag a lot of music that i have? because i don't like my music all messed up.

How has your organization/neighborhood/town/city/region/etc... used interactive web-based map tagging sites (ie, Google Maps, ZeeMaps)? I am exploring the potential uses of online mapping sites for the field of urban planning/design. Looking for specific...

I am having a heated discussion over tagging on the social sites. I think that tagging other people in photos on profiles (be it your own or other peoples profile) is to show ...show more

Of course, the primary factor is just that a search for my Internet name shows *far* more sites with a PageRank comparable to Quora (or higher than Quora). So it is something of my own doing. On the other hand, I like to keep a common Internet name to...