XML Visualizer for VS2003 (by yag)
One of my favorite features coming in VS2005 is debugger visualizers. They allow you to easily add a type-specific form based visualization while debugging. Beth points to the XML Visualizer on GotDotNet. It lets you look at your dataset in a number of ways - the data, the XML, the schema. Pretty cool.
I can't wait to see what comes when writing tools like these get even easier in VS2005.