Hulu announced a new subscription service called Hulu Plus Tuesday. The new service offers users expanded content, such as entire series of Buffy the Vampire Slayer, Law & Order, etc., that will be streamed in 720p HD, but even more importantly to Apple’s ecosystem, it’s the first and only way to watch Hulu streaming TV and movies on your iPad or iPhone.

On the App Store, you can now find an app called Hulu Plus. The app is currently listed as an iPad app, but the description specifies it is designed for both iPad and iPhone. It’s a free download, but it won’t stream content unless you have a Hulu Plus subscription.

The kicker for the short term is that Hulu Plus subscription is currently being offered only on a limited-access, request-an-invitation basis. Users can request an invitation from within the app or via Hulu’s Web site. As of this writing, we didn’t note any way to do so via the standalone client.

Hulu coming to the iPad is a big thing for Apple, at lease when it comes to Apple’s decision not to allow Flash on its iOS platform. Hulu’s service has heretofore been based entirely on Flash, including both the Web site and the standalone client. Offering an iOS app means that Hulu found Apple’s device empire attractive enough to invest in delivering its content using Apple’s development tools, and not Flash.

Count that as a strike of confidence in Apple’s decision to forego Flash.

Hulu plus on iPad

Above and beyond the iOS aspect of Hulu Plus, however, this marks the first time Hulu has tried to charge for content. A legal TV streaming service on the Internet, Hulu is owned by major media companies, including NBC, the first and only network to leave (and later come back) iTunes.

It was built on an ad-supported model, and the company has been inserting more and more commercials into its streaming content, with the goal of having as many commercial as broadcast and cable TV.

The service usually offers a limited number of episodes from current TV shows, however, and the movie selection is dominated by older titles, indie flicks, and B-movies. Hulu Plus will change at least the TV component by offering every episode of the major shows from ABC, NBC, and Fox, and a library of complete series from popular shows like Buffy that have had only a limited presence on the service.

All told, Hulu is boasting that it will offer 120 seasons and more than 2,000 shows in this library. The flip side of that is that it’s still represents only 32 shows (more or less), a small percentage of the totality of TV that is available.

In addition to iPad, iPhone, and iPod touch, Julu Plus will also be offered through Xbox 360, and various TVs and Blu-ray players that also have Hulu built into them.

The list of shows being offered: