Hypnopics is a great place to explore if you want some real gems in the genre, like bobjones said, but I prefer TFGames instead, though I've kind of reached the end of good content after a few years.
The good news is that TFGames has quite a few games involving hypnosis. Also, all transformation tags are clearly displayed in the search engine, so it's really easy to just skip anything you don't like. Another plus is that TFGames has quite a bit of variety in game engines, which, in my personal opinion, is a great way to avoid staleness.
The bad news is that there are a lot of unfinished games on TFGames, and that a majority of the games are HTML-based, a.k.a text games - some with, some without pictures. Also, these past few months especially, there has been a trend of people posting "games" which consist of barely an intro and 'can expect updates every few months (might delay to years)'. The authors of these "games" are basically just idiots who thought that by following a basic tutorial they could beg for money through Patreon.
I've enjoyed dozens of really good games on TFGames, but you'll have to sit down and filter through the crap to get to them.
By the way, I haven't played hypnosis games in quite a while, and my collection of games is not very organized, so if I have to name any games, it might take a while to search for them.