Is the 911 Twenty Dollar Silver Certificate from National Collectors Mint Really worth anything?

No. This is the not the first time this company has tried to profit off the 9/11 tragedy. They were shut down by Eliot Spitzer the first time, and I understand there is an investigation underway over this latest effort. They claim they are selling it for "face value," but there is no "face value." It is not legal tender, and it is very likely a scam.