http://www.shotcut.org/
http://libregraphicsworld.org/blog/entry/introducing-shotcut-a-new-free-video-editor
Long story short, Shotcut is not as good or capable, as a video editing app, as what you find for around $50 - $100 from companies like Sony Creative, Corel, Nero, Roxio etc., but it is better than most of the free alternatives, & it is in a class above every editor I've seen out of China from companies like Aiseesoft. Shotcut is keyboard shortcut based, it does not have a standard NLE timeline or story board, & it will use codecs you have already installed [so you're not limited to whatever's included like a lot of video apps].
Does that mean you should stop using whatever you're using now to move to Shotcut? Probably not -- if you've already found something that works well for you there's likely little reason to change what you're doing. Most free video editors amount to video converters that also allow cut edits [i.e. splitting/joining clips], whereas Shotcut is/was designed as something besides a video converter. It uses some of the same code as most converters, e.g. ffmpeg, but it's more than a front end or GUI intended so you never have to use the command line.
Installation is pretty low impact, though there are a lot of files that together take up almost 1/2 a GB -- there are very few registry entries, with nothing added to Windows or user folders.
