The stock 8800GT/9800GT cooler sucks.
Its loud, and doesn't cool very well at low speeds and if it gets any dust inside, it can only be removed by pulling the whole thing off. And the dust can make temps rise even more.
Heres what im gonna recommend, one of the best cooling solutions for the 8800GT.
EVGA | Products
It should be in stock very soon, its made for the reference 8800GT but im pretty sure the reference 9800GT follows the same exact design. Very good cooler, looks great and cools great too...and its very quiet up until 50% fan speed.