I've been very happy with the cheap-o grip clamps I've gotten from Harbor Freight. They have 'em on sale every so often, and a 12" clamp will go for under $5.00. I do enough work in the garage and in renovating properties that they come in very handy.
The picture below shows a "good"/expensive Quick Grip clamp (yellow) which was around $20-25 or so next to the $5 HF clamp. Yes, the expensive one is better quality - it grips tighter and is easier to release once it's on tight, but for me it's not worth the extra expense.
I've done similar clamping actions as described in the above posts using these clamps, although I'll typically use scrap angle iron or other scrap steel instead of wood.