My mother uses Ubuntu and likes it. I've also found Puppy and Sabayon to be great distros to give to grandparents, kids, and other people with no computer knowledge. Heck, I use Ubuntu MYSELF, because I like the fact that it's easy to use on the surface, but lets me hack away at things deep down. Mint is a good alternative to Ubuntu, but I find the Ubuntu guys are starting to outpace them. Good distro though.