Pokemon Showdown Beginner's Resources

StrategyDex
A comprehensive list of every Pokémon. Clicking on a Pokemon will give you information about it as well as tips and tricks for using it successfully.
Tier Statistics
Up to date information on what tiers you can use certain Pokémon in. For a detailed explanation about the tiering system, click here.
Damage Calculator
Allows you to calculate how much damage Pokémon will do to one another. You can also find this link by typing /calc into the chatbox on Pokemon Showdown.
Smogon Abbreviation Guide
A detailed explanation of the hundreds of acronyms scattered across the competitive battling scene.
Team Synergy Calculator
Calculates how a team matches up against individual types, both offensively and defensively. Effective for spotting glaring weaknesses.
Ultimate Pokémon Center
Detailed explanation of the inner mechanics of Generation Five.