Cocoa and notifications balloons.

Hi, there 🙂

Now I'm writing simple app which fetch data from my server. I want to show notification balloons like Gmail Notifier app (dark windows appeared at the top-right corner of screen). How I can do that in Cocoa?

PS. I know that I can use growl, but I wanna make really cool app, that doesn't require any third-party libraries (but can use them, if they are present).
PPS. I don't need compatibility with OSX < 10.5. 🙂
Thx for advice.
Best regards, Gleb M. Borisov.