Don't forget Epicor
Thats the three biggies, but there are many smaller software houses.
The company I work for uses one of these 'smaller' software houses for it's ERP, this actually works out quite well as rather than having to talk to the dreaded 'First line support' in India and go through a bloody crib-sheet when I have a problem or find a bug, instead, I can pick up the phone and talk to the programmer
who wrote the module in question.