Youtube is now using a new GData based API which doesn't need a developer key and is more customizable. You can now subscribe to your favorite youtube personalities using rss or atoms feeds. Just enter the youtube name you want to subscribe and copy the feed location.
The script updates itself every half-second.
Examples include using the live bookmarks on firefox, using sites like bloglines / netvibes or adding it to your google frontpage with igoogle, and using software like feedreader to get automatically notified when someone you subscribe to posts a video.