The can is to absorb fumes from the fuel tank, which prevents the tank from builing up pressure when it gets warm (primarily when the vehicle is not runing I believe). The carbon holds the fuel fumes until the computer decides to allow the fumes into the intake charge. In the olden days, these fumes used to vent to atmosphere, which is pretty harmful to the environment.
You can remove this system, but I would encourage you not to. You will not see any performance gains, will drop negligable weight, and may trigger the cel.
jason