I'm a huge fan of clever messaging within web apps. 404 pages and "down for maintenance" pages might be the first places one would think to revamp in a fun way, but I just noticed that twitter found a great way to make waiting a bit easier. 
This message pops up when searching your gmail contacts for people already on twitter. I've seen people complain about the wait for processes like this to complete, but twitter found a way to make the wait seem worthwhile. Turning a negative (waiting) into a positive (you must be popular). After all, how can you be mad at that?
Bringing a smile or chuckle from a user interacting with your site (especially during an obstacle like waiting for a process to complete) is a great sign of a positive user interaction.
