The latest stable release is OSGeo-Live 10.5 and can be downloaded from: https://sourceforge.net/projects/osgeo-live/files/10.5/
Picking the right image for you:
osgeo-live iso: 4.0 GB
A Lubuntu based bootable image, which can be copied to an 8 Gig USB thumb drive (faster and recommended) or DVD (cheaper). It can also be used to build a virtual machine from scratch.
osgeo-live-vm: 3.4 GB
This is a pre-made virtual machine (.vmdk), based on osgeo-live, suitable for use in VirtualBox, VMWare, KVM and other virtual machine applications. It has been compressed using 7-Zip.
amd64 or i386 architecture
ISO images are available for recent amd64 hardware (recommended) as well as older i386 hardware.
You can use the md5 checksum to verify the image downloaded successfully.
Minimum suggested system resources: 1 GB RAM (2 GB are better for trying Java based applications), 1GHz i386 or amd64 compatible CPU. No hard drive required. Mac users will benefit from a 3-button USB mouse.