This is one of the gems on my system. Whenever you have to create some AJAX interfaces, this tool comes in and supports you where ever you want. No matter if it is simple JavaScript debugging (with breakpoints) or stuff like modifying css, html or checking what messages have been send between browser and server. I love it ;)
Well, I am not the most experienced C# developer out there, but working quite a lot with ruby and RubyOnRails, the Dream framework is the perfect match for bridging these to worlds. Instead of complying with the sometimes overly complex way of creating tons of classes (ever tried to access the exchange 2007 webservice?), Dream provides a clean and easy way for creating and accessing REST based webservices. I really love it!