If you have followed my writing over at DavidJMoore.com then you will know my passion for Taking the Straight Line - getting from A to B as quickly and as simply as possible. I also have a passion for achieving great results using the base apps on both iOS and OS X. This isn't always possible, but when combining videos it is.
QuickTime X comes pre-installed on all Macs and makes it very simple to combine a set of video files. To do this all you need to do is open the video you want first in the sequence then select the rest of the files in a finder window and drag them onto the video that's open in QuickTime X. When you do so, you will notice some yellow film placeholders appear where you can drop the files you are dragging onto. You can then rearrange them as you see fit and once done hit File -> Export and you are done.