Vegas and Premiere are the two big ones. How extensive of an editing job are you looking to do here? There are basic video converters/croppers/etc. out there, but if this is a job, you'll probably want something a bit more pronounced, such as Vegas and/or Premiere. I know that my friend who makes stuff for YouTube (and else) uses Vegas.
The version of Windows Movie Maker that is available for Windows 7 doesn't allow for multiple timeline editing, which IMO makes it (almost) completely useless. Someone packaged up the last version of Windows Movie Maker that came out for Windows Vista, but sadly, while it does indeed contain multiple timeline editing, it isn't possible to save in HD video resolutions.
I never really liked VirtualDub. Never seems to go off without a hitch somewhere along the way.
Some burning software suites even come with built-in video editors now (Nero, Ashampoo Burning Suite, etc.), so that's an option too.
I'll look around and see what other freeware options are available. I don't really dabble in the video editing/creation aspect of things, so it's not really knowledge I can give off of the top of my head.
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