There are two pretty big web frameworks in the Crystal world right now, one is Kemal which strives to be the Sinatra or Flask of the Crystal world (lightweight, supporting plugins), and the other is Crystal which is trying to be the Ruby on Rails or Django of the Crystal world (full-featured, opinionated).
https://athenaframework.org is pretty unique. It's one of the more flexible frameworks IMO. It was inspired by Symfony and Spring, so takes a bit of a different approach as most other frameworks come from a more Ruby background.
I've long wanted to get into Smalltalk and this looks like a very nice, modern way of doing so.