I downloaded the game Hack RUN (downloaded the free version first) the other day and I've found it's really fun.
Reminds me of playing Uplink a number of years ago.
The basic premise is: You are a hacker that is hired to find info from a company. They give you some slight hints, a built in help system, and off you go. The interface is very much like a linux x-term (green on black) with a "mail" system and a web browser, including multiple (that I've found), very realistic web sites. You have to find usernames, passwords, and different systems to get into. Each successful new command, system, or bit of info gains you a new "level".
A very robust, level based hint system is also included with the game. Stuck on level 22? Enter 22 into the hint system and you have 2 choices: A hint, or the answer.
I like it a lot. Has anyone else played it? Are there any other games out there like it?