how-to block ads
Linuxiso.org is a place to start. They have a majority of Linux distribution ISOs (ISOs are CD Images) where you could download and burn or put onto CD.
iso.linuxquestions.org also maintains a list of ISO mirrors and bitorrents.
Also, you could download from each distributions web site, such as Red Hat could be found at »www.redhat.com and Debian could be found at »www.debian.org/.