Sometimes the market will not notify you of updates until you open the market, particularly if you either have it set to not notify you or if you have background synchronizing disabled on your phone.

Since I'm guessing you have not updated in a while, let the market continue to update your app list and check with it periodically and when it is done, update then.

If it continues adding updates, and the number of updates exceeds the number of apps you have installed, then go to settings --> applications --> manage apps --> all tab --> find market and kill it (press market, then press the force close button inside). Then, reboot your phone, and then try again.