well designed places of worship  

Piano's Padre Pio's town San Giovanni Rotondo
Nice place to pray, if its in your neighborhood.
http://tinyurl.com/ygdvg82

Another thought on the Padre Pio Pilgrammage Church...
I have never seen a building that is as understated and quasi inconspicuous on the outside and as impossibly brilliant on the inside.
It expresses something more profound about the real dichotomy between a truly religious person's outward calm and the extravagant structure of his inner world of faith than John Pawson's cliched revival can ever even hint at.
Yep, I'm still not persuaded by Pawson's monastery. 🙂
And add another feather in Renzo's cap.

Aalto
church at Riola, Italy

Bayonet Point, FL. Charles...
Bayonet Point, FL.
Charles Partin

How about Christ Church
The main building was designed by Eliel Saarinen and the school edition was the last building designed by Eero Saarinen during his lifetime.
And it's located two blocks from my house!