Question: Is there any opensource samples of JQuery usages of StackOverFlow-like sites...... 

Any help in this direction??

Answer: 
The web is full of them. For starters, I recommend reading through the [Documentation](http://docs.jquery.com/Main_Page).
It could help if everybody would just make a list of the plugins that are being used. For example, for plotting they use: [flot](http://code.google.com/p/flot/). For flot support on IE you need [excanvas](http://excanvas.sourceforge.net/)... I kind of feel this question has been answered before though...