I did some contracting work and then switched to salaried and then some side stuff with the salaried position. As long as you keep the side stuff hush hush, outside office hours on your own time, it shouldn't be a problem. Contracting was nice for a while, I could work whenever, but when I switched to salaried, I started to really like the structure office hours brought to my life. I could "leave work at work", once I put in the hours, that was it, no more thinking about it till the next day. Having a steady paycheck and various company benefits is a definite plus for me. And I find that within companies, the attitude you get from management and co-workers is a bit different if you're a contractor as opposed to an employee.
Someday we may need to activate the halo structure off Deerfoot and destroy the North East.