A good sway bar, clamps to upper a-arm mount, or frame just above that point and only requires a couple longer bolts or some clamps. On a Dedicated Race Bike we usally end up welding a set of tabs on the a-arms to bolt to.

Rath racing makes a really nice sway bar and a set of machined clamps to eliminate any welding. 

If you look at pictures of mine or Tim's quad of the month you can see the two different ways to mount them. He has a rand's I build mine my self, except for the one on the my 250 Im building now. That's a Rath, I got it to see if they were noticeably any better for the extra money they cost. I wont get another, they are nice because you can disassemble them mine are all welded and not rebuildable.
 
I wouldn't run one for trail use you will notice a much rougher ride than normal and you will also have less control. If all you going to do is run on seasonal roads it might be useful. but as a general rule anything rougher than that It wont help and you break links and bolts constantly.