AFAIK there is no comprehensive list of the default keyboard shortcuts.
The Quick Reference Card lists many of them.
You might find these handy:
PrintKeys.rb by Jim Foltz creates a printable list of your shortcuts.
printkeys.rbz (889 Bytes)
And there’s ShortCutsV2.rb which Thomas (tt_su) fixed for us a while back. 
shortcutsV2.rbz (237 Bytes)
Nonetheless, SU’s default shortcuts are merely a starting point for new users.
Experienced users tend to create shortcuts to suit their individual workflow.
At that point what is default and what is user defined rapidly becomes blurred and irrelevant.
What’s important is their shortcuts suit their individual needs and preferences.
I think most users would agree that the ability to setup shortcuts just the way you want is one of SU’s most powerful and endearing qualities.
-Geo