All of those things are being built yet, so we don't have much to link to. There are a few work-in-progress things, for example, the postgres adapter is coming along, and rust-graphics for graphical primitives. As we get closer to release, and as they mature, we'll feature them more.
> Will the cross-platform components from Servo be included in the Rust standard library?
As we already have a package manager, I think Rust will tend to have a smaller standard library, and encourage its use more. We'll see though.
> am right now working on a UI-driven app that will be deployed to Android and on the desktop.
We support Windows, Mac, and Linux as first-class platforms, and every pull request (and additions are all through pull requests) is tested on android. iOS coming soon.
This doesn't seem very performance-critical. I doubt the best tool for the job is C++/Rust/C.
To give you some background about the kind of apps I was referring to - I am right now working on a UI-driven app that will be deployed to Android and on the desktop. I am using C++, Qt and platform code where necessary.