I've had good luck using the Pedco products, the
Ultrapod and the
Ultraclamp.
The Ultrapod is great for attaching to pillars and stuff like that because of the velcro strap that can be wrapped around things that are too thick to clamp to. I also carry an extra long strap for fatter pillars.
The Ultraclamp is just a good lightweight, yet sturdy clamp for edges of tables, stands, etc.
Both make a great setup that gets you ready for just about anything. I think you could also get both for what you want to spend and maybe even have some left over. Shop around a little (use froogle or pricegrabber) to find the best price.