I am working with this stupid .3gp right now.
On my windows XP machine, I use "Free Flash to Video Converter" from "DVD Videosoft" to change it to an FLV output (use "Max Quality" in the output or audio and video sync slightly weird). From there, I use "FLV Editor Lite" to cut the video for time, etc.
I find it annoying that there is really NOTHING in terms of really good (and free) video editors for 3gp that I've seen. Nothing that 'does it all and does it well'. Unless you pay big money. Also - there's DEFINITELY nothing that I've seen for in-phone editing.
You would think with all the Android users out there, that more people would be interested in editing their videos? People just accept, and live with, garbage though. I suppose. :/
If anyone knows of anything better, please post!