Really exciting to watch the developments in OCaml/Reason web frameworks/libraries. I love the language and wish I could use it instead of Ruby for my personal projects at least. Others that have caught my interest are:
As follow-on work to Dream, I'd like to take a very hard look at how we do JSON server-side, to really make it much easier. Although this is partially solved by using GraphQL more :) Ideally, in the end, we will have a very fluent server programming experience.
Same goes for SQL prepared statements. I'd like to decrease the amount of boilerplate somewhat, hopefully without resorting to preprocessing.
This is part of the reason I didn't add too many helpers for either JSON or SQL to Dream yet - there seems to be considerable room for improvement here.
Sihl: https://github.com/oxidizing/sihl
ReWeb: https://github.com/yawaramin/re-web/
Of course, if you're interested in OCaml/Reason and don't know about Revery you're missing out.