Among several, Visual Studio.NET 2010 has a new feature that allows you to create nice directed graphs with a markup language called DGML (Directed Graph Markup Language).
Jason Zander provides explains the feature in nice visuals; while Cameron Skinner writes in detail of how it works.
If you are too much into the debugging scenario then, Mohammed Mahmoud has a debugger-extension that takes the output of !gcroot and creates a graph that one can interact with easily in Visual Studio 2010. If this feature sounds cool then this discussion is a must go-through.