I used to use very inexpensive products and spike the wash with a half-cup or so of borax or washing soda.
I've been trying to use better-quality detergents these days, since I wash a lot of stuff with cold water only. IMHO, these types of additives don't work well in cold, soft water, and may in fact damage my machine.
What I DO like to use is 1/4-cup powdered Snowy bleach with Wisk liquid if I have white or light-colored dress shirts to wash (but I might even stop that, since I picked up two different kinds of Persil today!)
Believe it or not, I actually think borax and washing soda are actually more useful in the bathroom, on bathtubs, faucets, and the like, then in the washer....