4th Generation Attack Changes

Vine Whip - PP is now 15 instead of 10. Yeah, I didn't ever understand the 10 PP limit. It's not like Vine Whip is all that good. 15 is still kind of unreasonable, but moreso than 10, at least.
Hypnosis - Accuracy increased from 60 to 70. Makes the move more useful, for sure.
Absorb, Mega Drain, and Giga Drain: Increases in PP: 20 to 25, 10 to 15, and 5 to 10 respectively. Good thing, too, since their low PP was kind of a downer compared to their power before. That said, Drain Punch is stuck at 5 PP...
Zap Cannon - Power increased from 100 to 120. For some reason likely related to the fact that a certain family of Pokemon can use the move with 100% accuracy, Dynamicpunch's power is unchanged.
Flash - Accuracy increased from 70 to 100. Big improvement, and makes the move... kind-of sort-of useful. You know, considering that normally it's only used to light up dark caves and all...
Bide - Something I noticed, but Bide now has priority over most other moves. Keep that in mind.
Petal Dance - Power increased from 70 to 90. Makes it one of the more powerful Special Attacks available to the Grass type (beaten only by Solarbeam and Leaf Storm).
Outrage - Power increased from 90 to 120, making it the deadliest physical Dragon move out there. Considering that a fair number of Dragons have high Attack... yeah.
Bite - Chance of flinching increased from 10 to 30 percent. Makes the move deadlier on a fast Pokemon.
Leaf Blade - Power increased from 70 to 90, PP increased from 10 to 15. Now it's as powerful as Crabhammer (with more accuracy and PP) while having the usage of its fellow crit-happy moves Night Slash, Psycho Cut, and others.
Jump Kick, Hi Jump Kick - Power increased from 70 to 85 and 85 to 100, respectively. If missed, recoil is now 1/2 of damage that would have been dealt. Which means, the move is now extremely powerful, but has also thus become much riskier to use. Could be fun, but has also been the number one reason Drifblim has so many Medicham defeats where it did not have to use a single attack...
Crunch - Now decreases Defense instead of Special Defense. Makes sense, since the move switched from Special to Physical. (On a similar note, Shadow Ball's effect of lowering Special Defense remains, but since Shadow Ball is now a special attack, that effect is now of actual use...)
Rock Smash - Power increased from 20 to 40. Makes the move somewhat useable early game, or on a Technician.
Sky Attack - In addition to being a two-turn attack and having a high critical-hit ratio, the move now has a 30% chance of flinching. A nice bonus to an attack that will only ever be used with the Powerful Herb as a one-time shot.
Metronome - A strange (but somewhat understandable) addition to the exceptions of this attack: it will not use any move the user already knows. So unless you decided not to teach that move to it, you won't ever get Psychic out of a MetroMew's Metronome.
Disable - Accuracy increased from 55 to 80. Makes the move... marginally more useful.
Spite - PP removed is now set as follows: if the user strikes first, 3 PP is lost. If the user strikes second, 4 PP is lots.
Sandstorm - A nice bonus here: when active, Sandtorm increases the Special Defense of Rock-types by 1.5-fold. This can definitely play into some strategies.
Fly, Dig, and Dive: Power increased: from 70 to 90 for Fly, from 60 to 80 for Dig and Dive. Very helpful in-game, where the moves now have usability and Fly now has some compensation for its not-perfect accuracy compared to Drill Peck.
Stockpile - In addition to its normal effects, Stockpile now also increases Defense and Special Defense by 1 level for each Stockpile. A helpful way to compensate for the time wasted in, you know, building up those Stockpiles, and you can just leave them in the Pokemon's mouth as a defensive wall if you want... Just remember that those boosts get reset if you Spit Up or Swallow.
Nature Power - Some changes in the moves switched to. Grass and tall grass now use Seed Bomb, caves now also use Rock Slide, roads now also use Earthquake, all water surfaces now use Hydro Pump, marshes use Mud Bomb, ice uses Ice Beam, and "plain ground" now triggers Tri Attack.
Charge - Now increases Special Defense by 1 stage. Could come into play if you think the opponent needs two hits to go down and you want to soak up one attack, but be careful as it still tips the opponent off that you're going to attack next turn.
Taunt - Now lasts for 3 to 5 rounds. Yikes.
Ingrain - Somewhat subtle side effect, in that if the user of this move is part-Flying or has Levitate, Ingrain will make that Pokemon vulnerable to Ground-type attacks (and associated moves). Strange effect, but it really only comes into play in two circumstances: Carnivine, or if Smeargle Baton-Passes the effect to a Flyer or Levitator. (And in the former, Carnivine resists such attacks anyways.)
Secret Power - Additional effects have changed as follows: Regular grass (and tall grass) can cause Sleep. Caves (and rocks) can cause flinching. Snow and ice can cause freezing. Roads (and sand) can reduce Accuracy 1 level. Marshes can decrease Speed 1 level. All water can decrease Attack 1 level. Default is paralysis.
Camoflauge - The only change I can see here is that, yes, Camoflauge can adapt to an Ice-type in snow.
Weather Ball - It should be noted that fog does double Weather Ball's power, while leaving it Normal-type.
Surf - Something to watch out for here: in Double Battles, Surf now hits your teammate as well. Best pair with a Water Absorber or someone with Dry Skin.
Blizzard - Just like Thunder would always hit in rain, now Blizzard always hits in snow. Could be really dangerous if planned correctly.