The first link looks just like an aerosol can: I don't know how you would be able to control it without spraying out a ton of CO2 at once. But then again, there may be a valve or something.
The second link is just a glorified DIY CO2 kit. The only nice thing is the CO2 ladder, which holds the CO2 bubbles down in the tank so they can diffuse into the water better. I think a DIY hooked up to an airstone/chopstick would give you better diffusion (personal experience with this kit).
The third link is essentially a mini paintball kit. Those are nice because the 20g tanks can be purchased in the air rifle secting of WalMart or Bass Pro for like $12 for a 25pk. What sucks is that the tanks will burn out fairly quickly, meaning you'll have to change them quite often (so the kit will cost you a fair bit in the long run).
Just like Tyler said, if you want to go all-out, get a regulator/tank from Craigslist. You can even find the normal paintball-sized tanks (24oz, etc.)with the regulators for fairly cheap.
If you like messing with your tank a lot, then a DIY CO2 system works just as well, but you can't really control the flow rate of the CO2.