Today I decided to check out the jQuery support within Visual Studio 2010. I had been having difficulty in getting IntelliSense to work correctly in Visual Studio 2008 SP1 as described by Scott Guthrie here. Turns out that VS wasn't allowing jQuery and jQuery UI to play along nicely. If I removed the script include for jQuery UI, IntelliSense would begin functioning for jQuery as it was supposed to. However, I'm currently trying to learn both of them so I want it to work properly.
After firing up Visual Studio 2010 Beta, I created a new Web Application Project:

By the way, you might be happy to see that the option for a website has been removed and you're now forced to choose a web application project. Personally I'm glad to see this.
Getting back to it, I immediately went into my code behind and started typing up a script block - I didn't see anything any jQuery IntelliSense at all. DOH. jQuery is SUPPORTED, not PROVIDED. After including the scripts for jQuery and jQuery UI, IntelliSense began working beautifully providing support for both.
For jQuery ...
... and for jQuery UI ...