Black Hat World is by far the most popular and aside from its name, it is full of information for White, Black, and Grayhat methods of SEO, PPC, CPM, and anything else relative to traffic for your site. You can literally spend hours just going through the various topics and reading the threads.

Here is a breakdown of what those colors mean:
White Hat: White hat is the Mary Poppins of SEO. Its fully manual work, going through and doing your account setups by hand, building backlinks by asking for permission of the site owners, hand writing blog topics, press releases, and viral video submissions through a single account.

Black Hat: Black hat is typically about automation. Lets not confuse this term with anything considered Malicious against a website or competitor. It's not about that and is highly frowned upon by all communities. Black Hat, using scripts and tools that give a website massive amounts of attention very fast. This used to be an outstanding tool that almost every major website was doing once news broke out about how effective it was, however Google cracked down in 2012 with the Penguin and Panda updates that put this to a screeching halt.

This isn't to say that black hat is dead. There are methods of using it and ways to benefit the website indirectly, which I will explain in more detail for the Advanced SEO Play. But for now, just understand the terminology, skip Black Hat methods, and focus on White and Grey.

Grey Hat: This is the cloudy area in between. It hybrids manual and automatic. Sometimes it asks for permission of sites, other times it just builds them without permission without being 'spammy'. Technically, any person doing any kind of backlink building on external websites is considered Grey hat. Google thinks that a website is going to miraculously get 1,000 of links pointing to them based on keywords that you are targeting; so this is why I declare this and many other items as Grey hat.