The classic on this was Great Cleave and Whirlwind Attack, and the bag of chickens: Loose a small flock of birds near an opponent. Whirlwind attack, striking at each bird. When you kill it, Great Cleave into the actual opponent, effectively giving you some ridiculous number of attacks on the real target.
Except that Whirlwind calls for a full round attack action, and allows for no other attacks, such as the Cleave attacks.
So look out for that kind of creative BS, but otherwise, yeah they stack.
Just so everyone is on the same page, the bolded portion is only true in 3.5. That caveat did not exist in 3.0... which is when that trick was created. It wasn't illegal "creative BS" at the time it was discovered and used.
As I said I would do, here are a list of monsters that are simultaneously using two or more feats (usually Power Attack and something else) in their stat blocks at the same time, from the MM3:
Boneclaw (PA & Imp. Nat. Attack)
Demon: Sorrowsworn (PA & Combat Reflexes - note that PA specifies that the penalty/bonus applies for the whole round, including AoO's... if you could only use one or the other, it would need to list another attack line for use with Combat Reflexes)
Drowned (PA & Imp. Nat. Attack)
Dust Wight (PA & Imp. Nat. Attack & Imp. Crit)
Mivilorn (PA & Imp. Nat. Attack & Imp. Crit) -> This one is important because there are two examples, one that has Imp. Nat. Attack, and one that doesn't, showing that the advanced one gets to add it to the other two feats, and the effects of all are shown in the same attack.
Necronaut (PA & Imp. Nat. Attack)
Odopi (PA & Imp. Crit)
Quaraphon (PA & Imp. Crit; PA & Imp. Nat. Attack)
Rage Drake (PA & Imp. Nat. Attack & Imp. Crit)
Salt Mummy (PA & Imp. Nat. Attack)
Ssvaklor (PA & Imp. Nat. Attack [x2] & Imp. Crit)
Nycaloth (PA & Weapon Focus & Imp Crit)