Pokemon Showdown Beginner's Resources

Originally written by verbatim and updated by Scene.
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.
SweeperCalc
SweeperCalc is an advanced damage calculator best used to view how your entire team matches up against your opponent's. To use, simply import your own team and input your opponent's Pokemon into the respective teams. From there, you can either select a set based on usage or input your own data for your opponent's team's specific Pokemon.
bReakMyTeam
Another SweeperCalc tool, bReakMyTeam allows you to easily view how weak your team is to common Pokemon both offensively and defensively.