My Druid always takes the form of a great white bear, but that's just choice and adds character flavour. As others have said, you can be any beast you want. Note that it says explicitly that some item manipulations will be beyond you. This is especially true for skittering sneak and the flying 'shape powers.
Also, you can't use non-beast form powers in beast form, and you can't use beast form powers when you aren't wildshaped into a beast. This means that a druid will have to do at least some planning in combat, as well as dabble in both kinds of powers, if he wants to be effective.
Giltharin: I would have made him change back, or argued that if he really wanted to open the door in beast shape he would have to make an acrobatics (or thievery or somesuch) check to manipulate the door open without hands.