Algae has all kinds of uses. A chef wants to grow it for food for people, and in the video above MIT built an algae photobioreactor which was used to gobble up CO2, and is now part of a biodiesel plant. You can make your own home photobioreactor to grow your own algae (its kind of like taking care of a saltwater fish tank). I am not sure how practical it is to eat algae (except maybe in sushi), but I think CO2 removal and fuel are real winners.
This is an interesting video below, of a guy that makes regular old gasoline out of algae that he grew. Same polluting fuel, but totally renewable, which begs the question... why are we fighting wars and drilling for this stuff? His website is very informative as well. I guess Bill Gates thought it might work and has invested in a company that promises to produce 10,000 barrels a day of this stuff - Green Crude.