I have to jump in here and correct this. The map showed the city closed below 14th St. That was the case for only the first few days; then the "frozen zone" was moved considerably south to Canal St., with only residents and people who worked in the area allowed in. Since then, areas areas closer to Ground Zero have progressively been reopened. Stuyvesant High School (which was practically in the shadow of the towers) was expected to be closed for several months, but reopened this week instead.
So yes, the area's taken a huge financial hit, and there have been many people displaced (some still can't get into their apartments, and some may never be able to return), and there's transportation difficulties because of the damaged subway lines, but most of the businesses are open and people have returned.
I'm not exactly sure what area the "frozen zone" covers today, but it's much smaller.