To edit simple movies I've been using Avidemux. It is a nice program that will work to do all sorts resizing, appending, adding a logo or changing from AVI to mp4. But mp4 files do not autostart, they have to load all the way before they play.SOoo, we had to add Handbrake to the mix. Handbrake does an excellent job of making m4v files. M4v files start when you click on them.
Then I discovered that the Pentax Kx takes excellent avi movies that I can make into m4v files, 500 meg files compress to 10 meg. My 'disposable' camera (I carry a $200 camera with me, that is how I catch some of those cool shots) only captures movies in mp4 format. That is proving to be very iffy to append or edit. It looks like Avidemux is going to fix that in their next update. Both Avidemux and Handbrake are opensource. But video editors are kind of like learning Greek, in Spain.