Cool, MetalScyther posted some already so I don't have to work from scratch.

PX made another cool Venusaur set if you've got enough time and want to concentrate on Special:

Double-Edge, Mega Drain, Growth, Sleep Powder

For Blastoise, since it doesn't have STAB and its Special is lower than Starmie's, it's better to have Blizzard over Ice Beam. Even Starmie's Ice Beam doesn't do enough damage.

On Charizard, remember that Slash's Critical Hit in RBY ignores the Swords Dance boost, so only Earthquake works off the Attack ups. Slash can cut through Reflects and Barriers, though. Personally, on my Charizard, I prefer Body Slam to use to shoot at those Starmies who switch in to smack him... It'd be fun if they get paralyzed, you know?

Mewtwo has lots of options, the best of which revolve around Amnesia, recovery, and special type offensives...

For Articuno, realize that Blizzard does more damage than Bubblebeam to a Rhydon.

Zapdos also has the option of Light Screen, but Reflect or Rest are probably preferable, especially if you want to annoy the heck out of any Tauros you may be having problems with. Zapdos kills Tauros.

If you're going to use the set MS suggested for Moltres (basically the only option for Moltres; its move compatability SUCKS), just be careful about self KOing Moltres by draining all its HP with Substitute and Double-Edge.

I prefer Swords Dance, Earthquake, Softboiled, Double-Edge on Mew. Explosion may be handy at times when recovering is useless, but I'd much rather have something that can last longer.