Divx isn't meant to be edited really, it's a lossy codec. But you could try to make the best of it and convert your Divx videos to AVI or MOV to import them into a full featured editing app like FCP.
For simple edits using only freeware apps you might try messing around with VirtualDub combined with AVISynth
www.avisynth.org. AVISynth will decompress your video and frame serve it to VirtualDub on the fly and allow you to manipulate the video however you like and then re-encode the video.