Alright, I'm a freshman in college and also a film major, and last year I pretty much was in the same situation that you were in. My college sucks and pretty much required everyone to buy a dell, so stupid me went out and bought a dell. Needless to say, it's a piece of ****, and I got sick of all the problems with windows after about a month.
So I looked around and decided to buy a used iBook G4. I got a great one on ebay for $650. It's decent and I can run Final Cut Express on it fine, but rendering can be slow at times.
Now, for college you'll definitely want to have a laptop. You can bring it to class and take notes on it much faster than writing. It's also great if you're living in a dorm because laptops take up much less space.
As far as PowerPC vs Intel, don't get a PowerPC. I have PPC and it's decent for word processing and stuff, but rendering video can get slow. And forget about multi-tasking (Final Cut & Photoshop) or something, it can't really do it.
So, I would recommend you get a Macbook. Probably go with the 2GHz, upgrade to 2GB of ram (cheaper aftermarket), and if you want, get a bigger hard drive. Otherwise, you'll probably want an external drive for editing. And make sure you get the SuperDrive so you can burn your videos to DVD.
If you're patient and look around every day or so, you should probably be able to find the 2GHz Macbook w/ Superdrive in the refurbished section for $999 or so. And then you can upgrade your ram for $100 from newegg. This will last you at least until your junior year in college.
I really wouldn't recommend you getting a PPC desktop or something, it just seems like a waste. You'll probably end up wanting a laptop for college anyways, so might as well get it now instead of wasting money on a desktop and having to buy the laptop later.
So I would definitely recommend the Macbook. Save up a couple hundred extra bucks and then wait until the next Macbook revision comes out this summer. When that happens, you should be able to get the current ones for even cheaper.