Steven Fackler has a fabulous Postgres API at https://crates.io/crates/postgres , MongoDB has an official (though experimental) driver at https://www.mongodb.com/blog/post/the-new-mongodb-rust-drive... , and Armin Ronacher has Redis bindings at https://crates.io/crates/redis (which I can't comment on the quality of, but I assume they're great because Armin (the author of Flask in Python) is a boss at API design).

EDIT: Agh! Armin isn't the author of Requests. :) I'm mad at myself because I even went to the Requests home page to attempt to verify that before posting this comment, and mistook his name under "Testimonials" as an indication of authorship. :P Sorry Kenneth!