Actually Mac OSX is not Linux. Deep at it's core, it's based on FreeBSD, but BSD is not Linux.
For new users, Ubuntu is usually pretty good. Ubuntuforums.org has lots of helpful people. Personally it's given me nothing but trouble lately, and I have no idea why, as my two years prior experience with Ubuntu was quite positive.
Another distribution to consider is OpenSUSE. Lots of people like that distro and consider it pretty good for new users.