After recently playing around with dial modem access, I came across the http://arbornet.org/ website. This website offers free UNIX shell accounts, which is nice, as you can play around with a real production UNIX system. Registration is simple; and breaking out of the menu system into a shell is easy as pie. The one thing I noticed is that a lot of users have not locked down their home directories, allowing almost anyone to read and execute the contents. Note the directory listings in the following picture:
Granted, most people wont be storing anything important on these accounts, and anyone with root access (which could be anyone) has your files. However, why risk it? Remember to run chmod 0700 on your home dir!