Sony has held a few VU programming competitions, and an amateur one is currently being run, closing date sometime in July. If you want to enter, but don't know where to start, you need these VU1 tutorials!
The tutorials will cover everything I learnt in creating my first VU demo, starting by dissecting the basic sample that comes with the harness, then modifying it beyond recognition :)
Use the links over on the left to get started. Along the way, you'll need the competition harness, VCL, the EE User's Manual, the GS User's Manual, and the VU User's Manual. Get them somewhere you'll be comfortable to reference them from, and begin! I'm afraid to admit I actually printed mine out... those poor trees!
Note to native PS2DEVers... you can still enter the competition! You don't actually need a Linux kit to create the necessary files, but at the moment the only harness programs I have run on PS2Linux. In other words, you can write your demo without PS2Linux, but you can't run it! I believe someone is porting the harness to native PS2DEV, but I haven't heard any results yet... I would certainly be interested in a ported harness if anyone fancies the job! It should be very easy, the harness really doesn't do that much!
Also, you won't have access to the manuals that I'll refer to in the tutorials, and I don't believe that VCL is available yet outside of PS2Linux. Then again, if you're happy writing VU demos without the aid of VCL, you probably don't need these tutorials!