Here's the opening selection of the Windows Phone 7 store. Overall, there's a good selection, but as you can see Xbox games dominate in the early going.
Productivity apps are solid, but business apps seem a bit light for Microsoft.
The tool selection is interesting.
A look at the Zagat app, which looks like a must have.
Another app that is appealing is Neurons, which features a series of science items and TED talks.
Flashcards is another one worth checking out. Also seeHands-on with the T-Mobile HTC HD7 Windows Phone 7 smartphone and A Windows Phone 7 'review' from a non-reviewer.