I've been using the exactly the equipment that you can see in Chuck's two links (I bought it at the local home brew beer supplier). The best thing about it is that you can judge how much pressure is in the bottle by how firm it feels. On my first attempt I thought the cap was leaking because I left it in the fridge overnight and the bottle was partially collapsed the next morning. Then I read the instructions again. The correct procedure it to squirt some CO2 into the bottle until it's firm, then shake it. It becomes soft again as the liquid absorbs the gas. Then you give it another blast and shake again, repeating until it stays firm, then leave it in the fridge to chill. It works, but it's hard to get consistent carbonation each time. Also, since there's no pressure gauge, it's easy to overdo it. I punched a hole in my ceiling when the safety valve blew!
You'll go through a lot of CO2 cartridges if you're going to be making much soda. I plan on making a lot, so I'm going to move up to a larger CO2 tank with a regulator like this:
http://www.ebrew.com/Products_S/cornelius_ball_draft_system.jpg
but I'm going to still use it on 1 and 2 liter bottles while I'm experimenting with recipes, then I can use the same system with a keg and eventually a counter-pressure bottle filler.
Good luck,
Kellan