In reality, we know what most newbies that are asking about shell accounts are looking do. If you are looking to learn anything and if you are serious about learning it, then I highly recommend you go and build your own *nix box. You are admin and you can learn all you like on your own home network.
If you want to learn anything from the people here, then stick around and read a lot, cause there is tons of information old and new that just passes through these forums. Check out the tutorials, there is tons of info there. You really want to start learning things, then I recommend you get to reading RFC's on networking and the like. Further your reading with Security info, like that at http://www.securityfocus.com/ http://xatrix.org. Only then will you be prepped to actually know how to do anything. Learn how to secure a machine and you will be okay. Learn to destroy a machine and you will go to jail.
Any which way, if you are learning security realted stuff, the best thing you could do is build yer own *nix box.
Think about it.
Regards.