Not much happens in them....
Sidious finds a SIth Witch (the one that was supposed to be in Ep 1 that was in a couple of mags but got replaced with Maul) and sends her in a Sith Fighter to attack Anakin, then she retreats into hyper space. Anakin against Obi's objections follows her, it turns out to be a trap. They fight on Yavin in the temples and the only way Anakin can beat her is by giving in to his anger, he destroys her and yells out a loud scream of rage which echos through the temples. Flies back to Obi and says Obi was right for not wanting him to go, it was a trap.
Mace kicks fucking ass in it, he has to fight a whole droid army alone without his light saber and does some kung-fu force shit that I wish he did in the movies. Imagine StreetFighter with the force.
Grevious kills a bunch of Jedi, including one that looks and sounds like the dopey guy from Scooby Do.
Padme and Yoda foil a plot to destroy the cave Jedi's get their lightsaber cristals from.
And ermm... thats all I can remember. Its nothing that directly contributes to the story of the movies, just some filler type fighting.