Have you recently started a new job or project where you need to get up to speed on an existing code base rapidly? Earlier versions of Visual Studio added features like the Class Designer. Now, VS 2010 provides several more tools to assist you.
View Call Hierarchy
“Find All References” not cutting it? Somewhat like a design-time call stack, the call hierarchy helps you visualize program flow much more easily.

A bit of trivia: View Call Hierarchy will only let you drill down into a recursive call once before showing the message “Further expansion is not supported for recursive calls”.
Sequence Diagrams
Here’s another context menu item that you can get by right-clicking on a method. You can reverse engineer your code to get an automatically generated sequence diagram.

Incidentally, this screenshot also shows another cool feature of VS 2010: detachable tabs. You can even detach code tabs.
Reading code that you didn’t write (or wrote a long time ago and forgot how it works) is one of the biggest challenges facing developers. It’s nice to see Microsoft building a solution to this problem into its flagship development tool.