It depends what you're trying to achieve - what do you want the Handler \ Module to do?
Up until recently, we've been using the MVC framework to provide RESTful services - it's really simple to setup & maintain, performs well and has everything we need.
Otherwise, you may want to look at the new Web API in .Net 4.5
Creating a REST service using ASP.NET Web API
Alternatively, you can have a look at ServiceStack - I hear good things about this, but haven't used myself