When you say 10 minutes, do you literally mean more than a minute, or are you being excessive? If you connect to the internet via Airport, depending on your preferences, this can cause the wakeup to take ~10-15 seconds instead of being instantaneous -- the screen is blanked or locked (depending on your config) while the network is being probed and a connection is being established. If this is the case, you can tell because the computer will wake up a lot faster with Airport off.
But if it's more than a minute...
1) Repair permissions while you're booted into the system and repair the disk while booted off the install DVD (or use fsck for the latter).
2) Reset the PMU / NVRAM / etc (see the Guides here)
3) Create a new account and see if the problem happens for the new account (if it does, it's a setting file in your account)
4) You could try an archive and install if nothing else works.
5) If none of 1-4 works, it's almost certainly hardware.