Linkage: http://www.stepmania.com (Mirrors included on site).
Note: "Do-It-Yourself" kit, downloads available separately.
=========================================
For the 3rd Gaming Download of the moment, I thought I go with something a little more "module" & Stepmania just comes to mind!
Stepmania is a DDR / ITG / PUI simulator, which means that you could use it to play the official songs from the games OR make your own songs & steps to make it an original gaming experience.
I will warn you that Stepmania is a "Do-It-Yourself" deal as the game itself doesn't include any songs or extras, but they DO have them available as separate downloads on their site as well as other sites in the "downloads database". This way you can pick & choose what songs / Themes / Announcers / ect. you want.
Stepmania requires a fairly modern computer with a decent video card. I know it may seem a little excessive, but when you tack on all the extras, your computer will need it... especially for computers under 1 Ghz. If you have a 800 Mhz computer w/ 256 MB's of RAM (or more) & a 128 MB video card, you'll do just fine.
Stepmania is available for Windows, Mac, Linux & even XBOX (don't ask me how)... For Songs (Official BEMANI & Original stuff), check out the download section.