An exciting WWW site developed by Frank Ruskey of the University of
Victoria contains a wealth of material on generating combinatorial objects
of different types, including permutations, subsets, partitions, and certain
graphs.
Specifically, there is an interactive interface which lets you specify
which type of objects you would like to construct, and quickly returns
the objects to you.
For certain types of objects, programs which generate them are available by
ftp.
It is well worth checking this out at
http://www-csc.uvic.ca/home/fruskey/cgi-bin/html/main.html
His home page contains pointers to other useful material on generating
combinatorial objects, along with interesting graphics.