Need a software to help you remove the undesirable scenes from your movies before giving it to friends or family? If so, then Avidemux is for you. Avidemux is an open-source and free software that lets you cut your movies in a very easy manner, you can simply load any movie, specify the start and end points, cut them and save! That's it! It's totally opposite to Windows Movie Maker (although I like this software, but not for this purpose AT ALL). It just removes the scenes, no loss of quality, no format change, nothing!
By the way, it's available in the Ubuntu repos by default, but 2 versions exist; The GTK+ version for GNOME users (e.g. Ubuntu), and the Qt one for KDE users (e.g. Kubuntu).