Blades of Avernum is a single-player RPG for Windows and Macintosh. The linked website does a better job of describing it than I can, but basically it differs from most games in that it was created with the specific intent that users could create and play their own stories and adventures. In the five or so years that Blades has been around, a sizable amount of high-quality user "scenarios" have been created, resulting in hundreds of hours worth of play-time.

I have been working with Blades since it was released, and in that time I've created 6 scenarios: A Good Beginning, Twilight Valley, El Presidente, The Empires' New Grove, Kingdom Hall, and Phew For A Minute... (PBTF). I've also created a (very small) handful of custom graphics.

At the moment, I am working on several projects, which can be found on the Upcoming Projects page.

    SCENARIOS:

A Good Beginning - "A remote island, a magical portal, a murder, and you."
                                1 outdoor section, 3 towns.
                                For levels 1-5.

      Twilight Valley - ""In my own strange way, I've always been true to you... In my own sick way, I'll always stay true to you.""
                                1 outdoor section, 8 towns.
                                For levels 1-100 (no combat).

        El Presidente - ""I'm just a man...""
                                0 outdoor sections, 1 town.
                                For levels 1-100 (prefabricated party)

        The Empire's - "Honour Amongst Thieves..."
          New Grove    1 outdoor section, 3 towns.
                                For levels 1-5 (though 5-10 may be more appropriate depending on difficulty level)

      Kingdom Hall -  "(no description)"
                                0 outdoor sections, 3 towns.
                                For levels 1-100

       Phew For A - "Go and tell the king that they sky is falling, when it's not, maybe not, maybe not."
             Minute...    0 outdoor sections, 1 town.
                               For levels 4 - 22.