Sources of realtime spatial data

Why not just build your own? One of the coolest personal geo projects was to grab a cheapo cam, project the georeferenced frames to a 3D scene from a building, combine it with OpenCV for auto feature detection and feed that data to postgis.

http://www.google.com/url?sa=t&source=web&cd=1&ved=0CCwQtwIwAA&url=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DUUU5xSeSaHo&rct=j&q=youtube%20realtime%20projected%20video&ei=5Yk7TtCsAu7WiAKWuuzbCw&usg=AFQjCNHVemjcnCt02aj3PDqeHxEqoTwCTQ

I was getting more data than could be handled by a non-event based server, but it made for a cool realtime video.

Another out of th box option is to use something like OpenGTS and attach it to something that moves :)

Have you tried looking into live bus tracking or similar AVL data?

A quick google search revealed a lot of possibilities, but the Chicago Transit Authority looked like it had possibilities. They even have a Bus Tracker API that might give you access to a direct feed (although I haven't even read the details, let alone tried to use the API).

How about global lightning data?

Another option would be to use Flickr REST API to fetch data about the latest uploaded geotagged images (if possible).

UPDATE: here's the Web method you could use: http://www.flickr.com/services/api/flickr.photos.search.html