The best way to learn how to use Linux is to use it. Pick something you want to learn to do (edit photographs with the GIMP, write documents, create a shared folder on your network, record a podcast for Hacker Public Radio, whatever) and do it.
There is a wealth of documentation at The Linux Documentation Project
. Some of it is dated, but that doesn't mean it's out of date.
About dot com
has a pretty good Linux site oriented towards new and intermediate users.
You can also find tutorials on YouTube, some better than others, by using the YouTube search feature.