Here are three good ones.
http://linux.about.com/. It's oriented to Ubuntu, but it's full of good info for new and intermediate users. Since it's a website, there are lots of pictures and stuff like that there.
http://tille.garrels.be/training/tldp/. Machtelt Garrels Intro to Linux. Excellent.
http://www.slackbook.org/. Slackware oriented, but excellent on the basics, such as file structure, permissions, and the like.
There is a wealth of information at
The Linux Documentation Project.
