|Weber Smoker Mountain|
Hands down the best bbq smoker available in the under $400 price point is the Weber Smokey Mountain aka WSM. It's bullet shape is proven, reliable, and affordable.
I've had mine since 2001 and it's still going strong. It's compact, lightweight and functional. Charcoal goes in the bottom, a water pan in the middle and two cooking grates in the top half of the cooker.
|Weber Kettle Grill|
Some may argue with me that a kettle grill isn't really a smoker. They would be right - it's a grill with versatility to be used as a smoker too.
Using good fire control techniques, banking the coals on the sides (or purchasing an accessory from Weber that makes that part even easier) will enable you smoke ribs on the grill without an expensive smoker. Get a rib rack and you can smoke 5 or 6 racks at once.