Power Attack: If you attack with a two-handed weapon, or with a one-handed weapon wielded in two hands, instead add twice the number subtracted from your attack rolls.
This is a change from 3.0 to 3.5, and I'm not it's so much a case of getting it wrong as just didn't read it before. I'm not sure it would apply to anybody but Kory, laurie_robey's barbarian in jamesbarrett's game, because all the other big Power Attackers use a shield. (For that matter, Kory might, too.)
"Summon X" spells: These have a casting time of 1 round.
I don't know why, it seems pretty arbitrary to me. But we've been using these a fair amount lately, so I'm going to have to remember it.
Tumble skill: Lots o' changes.
This is another one that changed significantly between 3.0 and 3.5. This one we just have to get used to.
Grappling: *two pages of rules*
Yeek, what a mess. We're gonna have to set up "grapple night" some time just to practice with the grappling rules a few times.