Sears sells a highly rated (personal reviews and consumer reports) detergent at a amazing price. We buy one box about every 6 months and it is only $25. This a amazing savings. Ultra Plus ™ 26.4 lb. Powder Laundry Detergent w/ Stain-Fighting Formula
http://www.sears.com/shc/s/p_10153_12605_03209898000P?vNa...
I also use oxyclean on tough stains. I have found I can get almost anything out if I soak it in a bucket of oxy clean for 3-5 days. Be careful because colors will bleed. Also cheaper clothes (walmart and children's place clothes have started to fall apart after being soaked that long but good quality clothes like Gymboree and Hanna Andersson have survived many many soaks)
edited to add: I didn't mention that I have 7 kids and they wear fresh clothes each day (I do a lot of laundry). I know another large family which goes through only about 1 box a year. For those who have smaller families this would go even farther.