If you think that your going to develop more of an interest in making youtube movies then in my opinion you might as well start using to use some
proper film editing software that can grow as much as you can push it
This package from apple looks good, although it's not free it seems
pretty cheap for what you get and includes audio editing software too, something you will need of yo start to make more challenging films
Theres quite a few online video editors that you can use here
that page also suggests a couple you can download for free.
If you don't mind buying something then I use
this which allows you to make some pretty
professional looking films. I can u2u you a link to one I made with it on youtube, It's a little bit adult in nature though so I can't really post
it here (No nudity or anything just someone talking about corsets)
If your really going to take it seriously then there are only one or two big names in video editing software. Final Cut for Macs and Adobe Premier and
Avid for the PC, the problem is that Editing software at this level is mega expensive around $1000 and you need a very good PC / Graphics card setup
to run it with multiple fast hard drives.