Let the hive mind of Engadget get that for you.
"I am trying to configure out a really dumbed down and intuitive PC for my grandmother. She recently had a stroke and while she is under my care I would like to repurpose a laptop for her to surf and email her children. Anyone have any experience with what input devices and UI's are really understandable for the over 80 crowd?"
>>Well, the site says "Yellow Dog Linux v5.0 for PLAYSTATION 3 will be made available through YDL.net Enhanced accounts, through the Terra Soft on-line Store, retailers, and public mirrors world-wide."
Yellow Dog Linux has a free downloadable ISO on their site, which is the same with every Linux distro. This is a requirement of GPL.
If you want the disk with tech support and documentation you can buy it from their online store (which is also similar to all Linux distros).
But its free.