Can you give more details on your budget, what kind of ideas you have for creating music videos and how deeply you wish to get involved in editing them.
For starters, you have iLife on your Mac (although you don't mention it, I'm assuming you have a recent Mac?)
So, with iMovie you can produce very good quality movies that can easily be uploaded to YouTube.
In terms of the camera... what is your budget? Are you looking to shoot HD video? There are so many options available it's hard to venture any kind of suggestion without more info.