Path of Exile Wiki
This website provides information regarding the game.

PoE Lab
This website provides information specifically regarding the Labyrinth.

PoE Ninja
This website provides information regarding the economy of the current trade league as well as an overview of all builds played

Zizaran’s Path of Exile University
This is a YouTube series which provides in-depth information on a wide range of topics featuring several known Path of Exile streamers

Path of Exile Subreddit
This is the official Path of Exile subreddit.

Path of Exile Builds Subreddit
This is a subreddit specifically dedicated to Path of Exile builds.

Grinding.Zone
This websites compiles a lot of useful resources and tools in regards to Path of Exile.

PoEDB
This website provides in-depth data regarding items, uniques, skills and passives.

PoE.re
This website allows you to generate search terms which you then can use ingame to find specific things faster when using the search function (e.g. in your stash or at the vendor)

Path of Exile Trade
This website allows you to search for items other players offer to sell in the current trade league.

FilterBlade / NeverSink
This website provides you with the option to completely customize your loot filter.

Awakened PoE Trade
This tool optimizes price checking items in the trade league significantly.

Mercury Trade
This tool optimizes trading significantly (this tool is no longer maintained but still works).

Path of Building Community Fork
This tool allows you to theory craft any kind of build.

Vorici Chromatic Calculator
This website allows you to calculate you how many Chromatic Orbs you will need on average to recolor needed gems on an item.