bitflags is a recently stabilized, fundamental library that needs its own home and maintainers outside the nursery. The plan is to set up a GitHub organization for bitflags with a team of interested folks, following the process outlined here. The more the merrier!
The level of investment required is pretty low, but if you're a user of bitflags or want to help maintain a key part of our ecosystem then please reach out here 
Thanks to rust-lang-nursery for shepherding rust crates to maturity.
Btw, bitflags seem to be single crate. Do we need an organisation for each crate ? Or is there some other reasoning behind this ?
Yeah it is better to create organisations for each crate or at least set of related crates (e.g. we have uuid & uuid-macro repos in the uuid organisation). We had a similar discussion earlier here.
I was drooling on something like python standard library or golang standard library that is quite comprehensive and ships with each language release.
Nevermind, since Rust enable us with the idea of re-exports we can have projects evolve independently and when we have a comprehensive set of tools and libraries they can be consolidated under an official crate of standard libraries (batteries included ) Something similar to core::Duration folded into std::time.
In my opinion, the secret sauce of GitHub organizations is teams, and how team permissions flow through other services, like publish permissions on crates.io and write permissions to Travis CI. Collecting multiple repositories under a single organization is absolutely nice, it's let the uuid org grow like @dylan.dpc mentioned with uuid + uuid-macro, but teams are a low-friction way to share permissions and seem to work really well even for organizations that just have a single repository in them.