The 1 Player Guild on BoardGameGeek is the place to start your search for solo games.
Beyond Solitaire is Liz Davidson’s great solo gaming website. There’s a blog, reviews and interviews with game designers. The reviews are succinct and very informative. As of 2019 Liz has started covering solo games for The Dice Tower.
BoardGameGeek is a resource for any kind of board or card gaming, solitaire or not. The site can be a bit daunting at first, but after a while you’ll find that you can’t do without it.
Box of Delights is the moniker of Richard Wilkins, designer of the exceptional cyberpunk game Renegade. Wilkins has made lots of solitaire gaming videos. I recommend having a look at his two-part Top 10 Solo Board Games. He’s also written an interesting essay on solitaire gaming.
Zee Garcia of The Dice Tower has made a video where he talks about his top ten solo games.
Rahdo, prolific board game youtuber and enthusiastic reviewer, has made a two part video where he and Nick of Board Game Brawl discuss their favorite solitaire games. Here’s a link to Part 1.
https://recommend.games/#/ is a game recommendation engine with decent filtering options (you can set number of players to one, for example). If you have an account on BoardGameGeek and have rated some of your favorite games the recommendation engine is particularly useful.
Singlehandedly is a good solo gaming blog.
Solitaire Times helps the solo gamer keep track of relevant Kickstarter launches, retail releases and related news. The site also features musings on solo games, recommendations and reflections on current topics. The site is run by solitaire table-top aficionados Athena and JW and I highly recommend it.
Try These Games is another game recommendation site where you type in a game you like and get recommendations based on that.
win-win is an online application that matches your BGG wishlist to games for sale on BGG and outputs it as a list with links. Useful!