Free Video Dub is a simple tool which can remove the unwanted sections of videos, without needing to re-encode the file and reduce its quality.
The program has a very basic interface, with no menus - just about everything you need is presented on a single toolbar. Essentially you must open a video (MPG, MOV, MP4, FLV, AVI and other formats are supported), select the left and right trim points of any given section, then press "X" to delete it. Repeat that for as many times as you like, click "Save Video" when you're done, and Free Video Dub saves the trimmed version of the file.
It's not always as simple as that, of course. The first problem appeared when we tried using the toolbar buttons to step frame by frame through our test video; the program actually moved in half second increments, instead. Would the built-in scene detection tool help? No, not really: Free Video Dub locked up when we first used it, and when it did work we still only saw the same half second resolution.
Dragging the selection point with the mouse did give us a little more control, though. We were able to use the program to successfully trim MPG, MOV, FLV, MP4 and WEBM videos, and the saved files all worked as expected (our unwanted sections were trimmed, but otherwise the videos played correctly).
Please note, the program will by default install a toolbar & other "extras" along with its own code. If you're not interested, pay attention during setup, choose the "Custom Installation" option, and clear the relevant checkboxes.