My absolute favorite feature of Visual Studio 2010, so far, is the javascript Intellisense support via the <reference> tag. Add the following line to your .js file and you get jQuery Intellisense.
/// <reference path="/scripts/jquery-1.4.1.js" />
My second favorite feature, so far, was just added with the Visual Studio 2010 Pro Power Tools just released by Microsoft the other day. It is the Add Reference Search feature. Behold…
There are a bunch of very cool features added by this small but powerful extension pack, but not having to scroll through a list of assemblies to find the one I’m looking for is a godsend.
You can read about all the goodies on the download page, but two other honorable mentions are:
Ctrl+Click is now the equivalent of right click and selecting Go to Definition. Booyah!
Ctrl+Alt+] on a selected block of assignments will align the = operator making your code block far more readable.
I highly recommend this extension. Thanks Microsoft!