I would like to know if there is QGIS version for a 32bit Mac (Intel Duo core processor). The newer versions require a 64bit processor.
As mentioned by danagerous, kyngchaos keeps an archive of past versions: http://kyngchaos.com/software/archive
QGIS 1.7.0-3 runs on my Macbook Pro 1,1 (32-bit Intel Core Duo) with Snow Leopard (10.6.8).
Alternatively, I've had success compiling QGIS 1.8 using MacPorts: http://www.macports.org/
It took a while to build all the dependencies, but once it's done you end up with a