How often should the intake be cleaned. As in the TB, the intake pipe, that sort of thing. I saw a bottle that I believe was even called intake cleaner.

I think I have also heard of GM top end cleaner which is supposed to be pretty good.

intake cleaner doesnt do a whole lot if your just spraying it in the intake, most people will suggest you remove the TB and take it apart, soaking it and cleaning it with the intake cleaner. Highly recomended, as most previous owners never did so.
You will loose a small ammount of coolant, and will need a new TB gasket.
Anyone wanna back me up on this one!?

That'* the only effective way to clean it. But remove the MAF sensor first, and DON'T use CARB cleaner.

gasoline worked fine for me. it smells good too

Yes, removing the TB & scrubbing the inside of the Intake with an old toothbrush works wonders! Just make sure the Intake Cleaner used is FI SAFE though! otherwise the other Carb Cleaner stuff will deteriorate your FI seals prematurely.
*NOTE: That'* a bad thing!*

As to the frequency of cleaning....I did mine EVERY spring! That way all summer long I had good horsepower.

VERY GOOD POINT!
It'* very important the MAF doesn't get any residue on it. The TPS is not as important, as I've cleaned them in the past w/o ill effects. The IAC should be cleaned too mind you, use a toothbrush & a little FI Cleaner or Intake Cleaner.