There are currently 3 releases of Accordian available. Accordian 1.0 is for Windows only while Accordian 1.1 is available for both Windows and Solaris (and you may also be able to port it to other operating systems such as Linux or MacOSX with only modest effort).
Accordian 1.0
Accordian 1.1 on Solaris
So how do you play? The object is fairly simple, you deal the cards out in a line and then try to stack them back up into a pile. To do this you may move a card onto another card that is of the same suit or face value, but only if there are either no cards between them or two cards between them, and you can only move a card towards the front of the line. It seems very simple, but if you're not careful, you will get stuck.
To download Accordian, goto the download page on SourceForge.net and choose the files suitable for your purposes. It's open source and it's free. *Please Note* Accordian 1.1 depends on some Qt 4.0.0 dynamic link/shared libraries, as well as a couple others, which you will need in order to run the program. On Solaris, the way I've compiled it, it should look for the Qt libraries in directory /Qt-4.0.0/lib/. For Windows it should be fine to put the libraries in the same directory as the program. Any problems, questions, or if you think you can make the project better, post to one of the forums, links to which are located here at the bottom of the page (at least that's where they used to be, although it seems SourceForge has removed project forums from the pages they maintain now), or email rsood@users.sourceforge.net.
Accordian 1.1 actually has a significant bug, which will prevent you from winning the game unless you correct it and build from source (the second while loop in checkWinLose in AccordianMain.cpp is missing the counter increment). I have been aware of this for quite a while, despite the fact that noone has filed a bug report or otherwise informed me of the issue - it does seem like a more likely reason for the download pattern mentioned in the next section, though. There will be a 1.1.1 release fixing that and other (minor) problems, after I have given it a thorough testing. If there is another release after that, it will be versioned 2.0, and will likely be Qt based. Notes on 1.2 can be largely disregarded, but if 2.0 comes into existence, it will probably have specific game generation capability (I've got code for that already that has been grafted onto the part of the 1.0 code base that had been going to be version 1.2).
Accordian 1.2 is in progress (slow progress, as I have work and other projects occupying my time as well). The code is Win32 because that is what most people seem to be downloading, probably due to the large dlls required for Accordian 1.1 (Qt version), or alternatively because they just don't know that the "Accordian-Qt" package has a Windows compatible version. Also, I have learned about something called WINE, which can allow Windows programs to run on Unix.