Walmart has decent sticks for around $20 but it takes two hands to adjust them. I personally think the Primos Trigger Sticks are outstanding. I always carried a plain stick with me but wanted something a little more stable for the long ranges shots I get coyote calling. They are the only stick I can dynamically adjust with one hand as I aim.

I can keep my hand on the forend of the stock and pull the trigger on the stick to drop it to the perfect height or adjust it on the fly. They go for $30-$60 depending on height and whether you want the bipod or monopod. The bipods are high enough to shoot standing up and are very solid. I really like mine. I've never had anything that good. The coyotes better watch out this winter!

I carry a set made by Polecat. I think they were around $35. They are sturdy, light, and collapsible down to a pretty small size. They do require two hands free to deploy from the collapsed position.

I carry a telescoping walking/shooting stick that I got for 20 bucks at dicks. It works excellent

I'm with Sourdough and Mr.Palumbo, the best ones I have found are the ones I made and painted myself. Varmint Al has a great step by step set of instructions on his web page.