I've been looking around to see if there are any good combinatorics tutorials done up as sage worksheets.
I see a couple of things, for example: http://sagenb.org/home/pub/3115/ and http://userpages.umbc.edu/~rcampbel/Computers/SAGE/combin.html
But something more comprehensive would be nice. If you know of one that exists, or if you have suggestions on style, so I can start building one myself, I'd appreciate it. Is there a good one for another area of mathematics?