I second the crock pot! On Sundays I buy ~5 lbs of chicken, toss it in the crock pot Sunday night, shred it all with forks in the morning (it falls apart, so easy). Then, I have a big tupperware of shredded chicken to draw from all week.
I also cook about 3 lbs of broccoli at a time.
Canned tuna is always handy.
I could keep stating the obvious.