Patch notes can be found here.
Alistar's main problem was his reliance on summoner spells to get into position because of his low base movement speed (300, the lowest there is). They changed his Headbutt so that it could target minions as well, which gives him the ability to get to a location faster in order to Pulverize another target or to escape by headbutting into a minion to gain some distance. His speed was upped by 5 as well. His passive was changed also. Before, it let him deal additional damage to buildings, which made builds based on breaking towers rather funny and effective (I even bought a full runepage of attack speed for it, haha). It did not really synergize with the rest of his kit though, so now it allows him to walk through minions for a few seconds after using a skill. This is really amazing because minion collision would always mess up what otherwise would have been a kill, and it also reduces his reliance on Flash and Ghost. Another added effect is that after he uses a spell, he Tramples, dealing a bit of AOE damage for a few seconds. One major problem for him was his inability to farm well, unless you didn't build entirely tanky.
Fiddlesticks changes were unexpected, for me at least. His Terrify range was increased, his Drain heals less and has a shorter leash, his Dark Wind bounces 5 times at all levels, and his Crowstorm's base damage was decreased while the scaling was increased. The Dark Wind changes were nice, it's actually useful in its early levels now. To make up for his lowered healing from Drain, his base stats were buffed so his jungling wouldn't be too harmed. You'll need 600 AP to make Crowstorm deal the same damage as before, however, which is a heckava lot for a champion that needs to be built at least slightly bulky to survive after he Crowstorms in. Haven't seen him in a game yet though.
Gangplank should've been reworked a long time ago. The devs got rid of denying minion kills yet Gangplank can deny with his Raise Morale. His Parley had its damage and cooldown lowered so he would be less of a one-hit wonder in a quick teamfight. Remove Scurvy was changed to be better at lower levels and not as great as before in higher levels, but it still gets the job done of removing crowd control. Raise Morale does the same thing as before basically, without the denying so it's actually easier to use as you would need to be near an allied minion to use it before. His Cannon Barrage was too reliant on RNG so now every enemy in its radius is slowed even without being hit by a cannonball. The damage, radius, and slow are reduced to compensate. One of the only reasons I played GP because his deny really gimped the other team's solo lane but we'll see how it goes as the week goes on.
Rumble came out today, sporting a flamethrower, shield/speed boost, slowing drills, and a new type of skill. Flamethrower just spits fire out in front of Rumble, but he can move while it is being cast which makes it great for chasing, not so much when you're running. His shield is fine, and the speed boost is amazing. His E can shoot twice in quick succession and the slow it applies stacks. His ultimate is a completely new type of skill, you drag from one point to another to create a wall of sorts that deals damage and slows enemies in it. This lets you set it up in many ways, such as blocking an inlet or dropping it in front of you so an enemy who chases has to go through the full thing. He runs on a new resource system called Heat. Basically, his spells generate heat and when he is above 50 heat, his spells are stronger. If he hits full heat, he is unable to use his skills until he completely cools down but his autoattacks are stronger. It's a balancing act to play him to his full potential, which means you'll see many, many bad Rumbles for awhile.
