It's a curious tradition in video game sports, but the NHL doesn't allow games to use all the third and alternate sweaters until they've been used in real life. Now they have, and EA Sports released the code unlocking them.
The code is: bcxkg8fkx3h4m3p5. Select "My NHL 11" from the main menu, then "NHL 11 Code Entry." The seven jerseys it gives you are featured below.