Flickr is a good example of how I can get pigeonholed on the internet and miss something great. I used Flickr to collaborate in picture editing game a year or two ago, but then I gave it up and can not even remember my password, because I always use Picasa (which I really do like).
Then I stumbled upon it again and discovered what I have been missing. I'll still use Picasa to coordinate with photoblogs, I'll add video to Flickr and use it to collaborate and communicate with a wider audience.
After we all upload we can head over to Big Huge Labs for a little Flickr fun.
Oh, and why not go mobile while you are at it.