Sam's Club is a working mom's best friend.

I love my Sam's Club.  My $40 membership (Advantage, not Advantage Plus) saves me $.02 per diaper--which adds up fast, when you've got two in them: we save something like $10-15 per month on diapers.  Same with Pull-Ups for the imp. 

Other advantages include insanely good meat prices, bread prices, and bulk dry goods prices.  Yeah, sometimes you're better off going with an off-brand, or a smaller size if you won't use the full quantity, but sometimes the name brand is enough better that it makes sense. 

One of the things that saves me a lot of time and effort is buying paper plates and bowls, plastic flatware, and the disposable aluminum warming pans aimed at restaurants (a pack of 30 cost about $10 or so, the last time we got them).  All minimize cleanup, and the pans are great to make a couple dozen casseroles at once for freezing to save time later. 

I just wish they carried minutes and hours one could buy--I never seem to have enough time.