Daylily, I am glad you started this, as I have been thinking of doing the same thing! I have read that the average US family spends $120 a week at the grocery store, but there are SO many variables! For example, my sister spends only $80 for her family of 4, but then they eat out A LOT, and the kids buy school lunches, etc. etc.
Here's the scoop on my family: I spend an average of $150 a week. There are 5 of us, and 3 kids ages 6, 3, and 13mo. I cook and bake mostly from scratch. This gets me mostly organic produce, fresh fish, meats, beer, disposable dipes for 2 (yes, I know!), loads of yogurt, butter, bread-making supplies, and plenty of beans and grains, coffee and tea. A few snack foods, too, such as corn chips and salsa, popcorn, hummus, and organic graham crackers. We never eat out, and dh makes his work lunches from this and I make ds' kindergarten snack from home, too. And we get WIC, so that covers much of our milk, eggs, cheese, and some cereals. All considered, I don't think we do too badly. When we lived in the UK, I spent slightly less, but I really couldn't get what I wanted with the money, because everything was so much more expensive. Within the budget I have stated, I get pretty much what I want, and I am very thankful to be able to do so.