Post the output of this command:
FWIW, wget is not installed by default on any Mac OS X versions.
And I know of no command named "shell", though I know of multiple shells.
If you're saying the problem is that you can't open a shell in a Terminal window, then it's quite possibly a botched shell profile file. To find out, you'll need to tell us what shell you're using (is it the default bash or something else?).
You could also create a new user account in System Preferences (the Account pane before Lion, the User and Groups pane in Lion) and try Terminal there. If that works, post again and we can give commands to help discover and/or change the shell profile in the malfunctioning account.
And please identify what OS version you're using.