ConwayLife.com

I am the 15th person to find xs21_gbaa4oz0d55d but it didn't put it in the "discoveries" page of my profile, the haul can be seen at
http://catagolue.appspot.com/haul/b3s23 ... 86ce6a75d8

That's because 21-bit still lifes are surprisingly common, and so are not considered notable. I think the discoveries page contains still lifes greater than 32 bits, but I could be wrong there.