pgRouting is available as source code as well as in binary formats (Linux, Windows, Mac OS X). If you want to install the current development version, check out the source from pgRouting Git repository.
PostGIS and pgRouting Builds (pgRouting v2.x)
Winnie Bot Builds:
You can find previous versions in http://download.osgeo.org/pgrouting/binaries/
pgRouting library and workshop are available on OSGeo Live DVD: http://live.osgeo.org
OSGeo-Live is a self-contained bootable DVD, USB thumb drive or Virtual Machine based on Xubuntu, that allows you to try a wide variety of open source geospatial software without installing anything.
You can find all the pgRouting Releases:
You can find previous versions in http://download.osgeo.org/pgrouting/source/