I was reading some of Ben Carey's older blog posts and ran across this reference to GhostDoc, a terrific commenting tool for Visual Studio.
Sure, hitting the slash key three times above a method or variable will give you a template, but GhostDoc takes that a step further by generating useful text to fill in fields for those comment templates -- including generating documentation for method parameters and return values.
GhostDoc looks at your method and variable names, infers a few things and plops in reasonable comments. It's almost a completely hands-off task to document if you've done a good job naming your methods, method parameters, and variables. (You haveread your McConnell, haven't you???)