Previous releases of Blender are available at http://download.blender.org/release. Here you can also find:
- the first 1.0 Irix Blender version
- Blender 1.60, 1.73, 1.80, 2.04, 2.25
- the 2.04 iPaq port.
- the last BeOS port, Blender 2.11
- web plugin players
On the Past Releases page most recent previous release logs are available, with splash screens, new features and fixed bugs.
Check also http://download.blender.org/source/chest/ for interesting source code from the past. it has old Blender versions as well as interesting in-house software from the company that developed Blender; dutch studio NeoGeo.