Below are a list of websites I have found useful for researching much of the information found on the site, as well as providing informative articles about the games history which I’d recommend checking out:
My Twitter for updates on this website. I’ll also try to post information about Retro and Retweet other useful content.
As far as retro articles go, especially for the WOTC era, Jason provides a very informative history of the game, as well as providing a good resource for old lists.
A great resource showcasing many lists for each year (usually Worlds format), as well as pictures of them completely built by Jimmy Ballard.
An active Facebook group dedicated to the discussion of retro formats.
An active blog maintained by Sean Worcester, with both articles and decks focused on Retro content.
One of the only resources which has a lot of information about what was going in throughout each year, as well as what people were discussing going back to the early 2000’s.
A more recent resource in the grand scheme of things, but one of the pioneers in providing lots of detailed content for the game as well as recording a lot of tournaments in the time it was active.
One of the first websites to dedicate itself to creating articles (and paid articles) from the top players in the game created in 2009. Also has a few topics about the history of the game and past formats in their forums.
Another forum with reports going back to 2009 dedicated to Competitive TCG.
A Wikipedia dedicated to Pokemon, and has lots of entries with information to past formats and events.
Full high quality scans of cards from every set, and a very useful advanced search feature which can search by format.
A website hosting a lot of information on HGSS-NVI format, including results, decks and ratings.
A Japanese blog reporting on Japan’s retro scene including Deck Profiles, Tournament Results and discussions.
A Japanese blog focusing on Base-Neo series, including a detailed look at the Palace format.
A Japanese Wiki on the TCG history in Japan. It includes both Half and Full Decks and gives a look into decks that were popular in their history. However the lists can be submitted by anyone and are often poor quality.
One of the only reasons a lot of the content exists on the site. I’ve used this to search for content on defunct official and fan Pokemon websites.
Feel free to suggest any more websites with useful information!