Refactoring duplicate code into methods
I've been working on a Resharper plugin that does what you are asking. That is, it scans your code, searching for sections that can be replaced by an existing method call. A section can be a whole method or just a part of a method. When it finds one, the lightbulb pops up and offers to replace said section with a call to the existing method.
(source: landofjosh.com)
I call it AgentRalph. At this point it's not ready for production use, but I've been making a lot of progress and hope to make a release soon.
Extract Method.