There's been a couple posts about that already. I'm all for biodiesel, against soydiesel!! There's a difference: www.energy.cas.psu.edu/soydiesel.html
I've been running a 2% soy biodiesel blend in my truck, can't tell the difference from regular, which is good. I've studied soybean oil biodiesel and ran tests vs. regular #2 for my senior design project at school. The soy biodiesel is, IMO, far better than regular diesel, has higher lubricity to help extend engine life, burns cleaner, raises cetane number, and meets Tier I & Tier II emissions standards as well all the other requirements set forth by ASTM. I think it is the best alternative fuel right now, and if we can get subsidies from the government to make it cheaper, there'd be no question about it.
I'm not for burning veggie oil, just don't trust putting something like that thru my engine. As mentioned earlier, there is guy that's been running it for a while with no problems, and I'm interested to hear how it turns out.
There's also the legal issue. I don't think you can burn veggie oil legally, but wouldn't imagine it to be too big of a problem getting caught.
But for now, I'm going to stick with my soy biodiesel, help my truck, myself and other farmers out.