Haar measure on a quotient, References for.

The book I always look at for such things is Nachbin, The Haar Integral, which is short, and has a whole chapter on Integration on Locally Compact Homogeneous Spaces.

And a plus: he gives you a choice of reading the proof of the existence and uniqueness of the Haar integral according to Weil or according to Henri Cartan.

Bourbaki's section on the Haar measure is one of the best sections on the Haar measure in any book, plus it's one of the best pieces of Bourbaki writing. This is of course because Weil played an integral (a pun for you!) role in proving the Haar measure in full generality.

You can find it in Federer Geometric Measure Theory pages 121-129.