I used to use a Brine Shrimp Hatchery that I got at the LFS for about $10. It was a small plastic box with an airline with an airstone and some type of screen I think. Worked pretty well.
I basically use the same one as kasakato linked to except I built a stand instead of the bottle inside bottle method because it was messy when trying to clean having the hose draped through the bottom and it was never too sturdy anyway. I just drilled a hole in the lid just large enough to force a flexible airline through and then silicone'd it inside and out and let it set up. Poured 1 liter of water in and made a mark on the bottle with a sharpie so I don't have to measure it anymore. I put an adhesive thermometer on the outside of the container and filled with water and added air to the mix. Then place a desklamp near the container and moved it closer or farther to get somewhere around 78-82 degrees. Not sure if this is optimum temp or not but it works pretty well. I add 1 heaping tablespoon of non-iodized salt and half a teaspoon of cysts (make sure you get good ones or you'll be disappointed). I think I should really be using saltwater salt instead but just havn't done so. After about 24 hours, turn the air off. I keep the light near the bottom of the container and they seem to congregate there. Once the eggs have floated and the shrimp have congregated, disconnect the hose and pour what you need into a cup. Mix with freshwater and pour through a brine shrimp net. rinse the shrimp to clean as much salt off as possible and then you can either swish the net in the water or you can dip your finger into the BBS and sort of measure how much you give each tank if you have multiples. KYle