Site for Simulink Projects?
Simulink comes with several sample models in \ Toolbars \ Simulink \ simdemos
Mathworks File Exchange can also be found for Simulink files: http://www.mathworks.com/matlabcentral/fileexchange/?term=simulink Unfortunately, many examples may require Simulink add-ons that you may or may not have.
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You have a list of models in each simulink toolbox. Take a look at the demos section of each toolkit, especially the DSP Toolbars and Communications Toolbar. Enter "demo" at the matlab command line and you will get a list of demos available in your version of Matlab. You can also look at the FileExchange Mtalab group for a few examples. Here is a link to the best simulink models http://www.mathworks.com/matlabcentral/fileexchange/?term=simulink&sort=ratings_desc
a source to share