Feral Hydra
: A simple 0/0 for 1+X that can buy more +1/+1 counters for mana. If nothing else it's a great way to sink your mana every turn. Without much in the way of non-creature spells its the best place to put it.
Genesis Hydra: Best saved for turn 5 or later when you can guarantee that you hit a card that you can play. It's unfortunate that a 0/0 can never be cheated in this way, but it's a good way to dig through your deck.
Hooded Hydra: A bit more interesting since you can either just hard cast him for any size or play him face down and Morph into a 5/5 for 5 (two mana cheaper over two turns for that size). When he dies he becomes a bunch of 1/1 snake tokens. Nice. "Hydraback Walker".
Lifeblood Hydra
: Our first Hydra with Trample is also the most expensive. Three green plus X isn't cheap, but at least when he dies you gain life. The high cost is mitigated by the abundance of ways to add more counters.
Managorger Hydra: If your opponent can't kill it dead then the Managorger will eat your opponent dead. Just give it time.
Mistcutter Hydra: Cheap and effective. The only Hydra with Haste and also comes with protection from Blue and cannot be countered. Solid.
Primordial Hydra: Damn, son. Doubling it's counters every turn is just insane. Probably not the best option on turn 3 unless you know it's safe. It would be a 2/2 on turn 4, a 4/4 on turn 5, an 8/8 on turn 6, and a 16/16 with Trample on turn 7. Hard to pass at any stage of the game, this thing can and will become too big to handle.
Protean Hydra: Another good and cheap Hydra that is a bit harder to deal with. Makes for a great blocker that becomes an even better attacker. The doubled counters are not added until the end step so if all of it's counters are removed it just dies. I wouldn't play him for less than two counters, but the more the better.
Scourge of Skola Vale
: 0/0 that is hard cast for 3 mana and two +1/+1 counters. If any of your other creatures are going to die, just feed them to this guy. Since the Scourge has Trample, this guy is easily one of the biggest and most menacing threats.
Vastwood Hydra: The last Hydra on the list is the Hydra that gives back. If Vastwood were to be eaten by Scourge it would gain twice as many counters. This is what Servant of the Scale is all about. Turns out he wasn't in allegiance with Dragons, but to Hydras.
