This trick has been getting a lot of positive feedback in the Yoshi's Island thread, so I'd like to make it more well-known.
1. Record footage of your game at 60 fps
2. Use a video editor to slow it down to 30 fps by making it run at half-speed
3. Make sure it is compatible with the HTML5 player (should happen automatically?) and upload it
4. Instruct viewers to view it with the HTML5 player, and increase the playback speed to 2x. The HTML5 player can be enabled by going to
http://www.youtube.com/html5
Here are some examples of youtube videos that are viewable in 60 fps (all thanks to Nintendomination):
Yoshi's New Island:
http://www.youtube.com/watch?v=c3VYsP_321g
Kirby Triple Deluxe:
http://www.youtube.com/watch?v=8oX1PWAYVy0
Donkey Kong Country Tropical Freeze:
http://www.youtube.com/watch?v=JkiY13LHYXw
Mario 3D World:
http://www.youtube.com/watch?v=X1ukHG6AgiE
Bayonetta 2:
http://www.youtube.com/watch?v=YP21RW0MiSM
Mario Kart 8:
http://www.youtube.com/watch?v=dRKECn7TxkU
I'd like to see this catch on, because youtube's 30 fps limit is downright archaic, and it would be great if Lets Players and even publishers had an easy way to share 60 fps footage of their games!