Only way to get the shutter count on the Mk3 is to send it into Canon as far as I'm aware.
I tried various programs and looked into it when I had one prior to selling but there was no way to get it.
You can't check with the MKIII onwards, however, all the tech guys seem to think that if your Canon has done more than 200 shutter actuations then it's either broke, or soon will be.
Not officiallyYou can check with the Mk IV