Big, complex, well-structured .R file for demonstration?

Hi List, 

I'm looking for a rather big, but well structured R file that contains
as much of R language features as possible (i.e. that uses a lot of the
functionality described in the 'R Reference Card' and, if possible, S4
classes too).

I want to check some code I wrote against such a file and use it for
demonstration purposes. However, most .R files I find out there are
rather short without much structure.

Any links to candidate (open source) files would be appreciated.

cheers,
Thorsten