jClass.extend() lets you build a class that extends one or more existing classes.
jClass.virtual() lets you construct a “virtual” class. That is to say, a class that can not be instantiated, but that can be extended by others.
Internally jQsimple-class uses some jQuery methods, but it does not depend upon jQuery to be used, a standalone version that bundles the parts it needs (not all of jQuery, and without exposing them to the public namespace) is available for applications that do not use jQuery. I have written an extensive testsuite for jQsimple-class to make sure that things work as they should, and it works across all modern browsers.
For more examples and the full API, see the jQsimple-class documentation. jQsimple-class version 0.1 is available for download now. Minified it is only 1.5K (or 9K for the standalone version). Any feedback is welcome, feel free to do so in the comments, or, if you find a bug, on the bugtracker.