Recently I was talking to a friend about Visual Studio 2010 - specifically about changes we were hoping to see. He had brought up how annoying it was to only be able to see 6-7 tabs in VS2008 before you had to use the dropdown arrow to navigate between source files. This problem is amplified even more with so many page types having corresponding codebehind files such as .xaml and .xaml.cs. I had told my friend that VS2010 was going to have wrapping tabs to fix this issue - I heard someone else voice this issue at a local VS2010 training event - but as of the last VS2010 beta there was no wrappable tabs ability.
Luckily Scott Hanselman tweeted about Tabs Studio - and it addresses both of the main issues with the built in tab control in Visual Studio - it allows wrappable tabs, and it groups your control parts together - what's more, the tabs are customizable with your own XAML.
(my custom tab style)
When I installed Tabs Studio I thought it was a cool idea, but after using it the last 2 weeks I'm hooked. Not having to look through all your open files for the corresponding XAML code behind goes a long way, and being able to maintain more than 8 open files (and have them easy to get to) makes dealing with large and modular solutions a breeze - and at $28 for a license you can't ask for much more.
Update: You can find the entire XAML definition here including how to change the close (X) icon, etc. for even more customization than shown in my example.