I'm no master but I can blow some pretty good O's. Never taken a video of it, although I should get around to it.
I like slowly exhaling a big cloud into a chilled glass. It's fun pouring it out of the glass on the table, the way it behaves in the air is really interesting to look at, and it makes for a pretty neat party trick (ie: take the empty pitcher and fill it up with vapor, then proceed to "pour a glass" from the vapor pitcher).