Yahoo! Messenger just released a new beta this week with a plugin SDK so that you can customize messenger and build your own single or multi-user application. Messenger plugins are based on HTML, so you can write them just like a regular web page. Since we all know the best sites are built in Flash, I fully expect the best plugins to go the same direction.

Once you get the beta, you will find two places for plugins. The first is the tab area of your friends list. For any Flash Lite developers, I think this should be an interesting area. The space your get for a tab is not too far off from the screen real estate for a Flash Lite app. While we are waiting for the OEMs to deploy the Flash Lite player, Messenger should be a good area to showcase your content.

You can also add plugins to your IM window. If you are a game developer, this is an ideal way to get to work with multiplayer concepts, and actually get your game played by a network of millions of users. Messenger gives you a LOT of hooks to pass data, do permissioning, and otherwise deeply integrate into the Messenger experience. Even if you aren’t into games, there are a lot opportunities for creating multi user and collaborative applications.

Since I first heard about the feature I’ve been biting my tongue from wanting to tell all the Flash developers I know about this.

Now, for the really cool part: let’s talk Flash versions. Use filters, blend modes, the external Interface; they will always be available. The Y! Messenger install process is now installing the latest version of Flash for those that don’t have it. Now it is up to you to get all of your friends on Yahoo! to show them your cool plugins and help Flash Player penetration at the same time.

Last month the winners were chosen for Red Bull’s Flash game building contest for college students, Red Bull Build. The student teams submitted game proposals, and the winning team is now building their game in a state of the art development studio built just for them in Orlando.

The team will be riding a red bull buzz for 21 days while making the game. During that time the judges from the contest will dropping in to offer some encouragement, advice, but mostly just hang out with the team. This weekend Jesse Warden and I will be there as the team wraps up their first week on the project. I can’t wait to see how it is going and hopefully will get the chance to post a few pictures.