Target is my "happy place" in the States, and Monoprix is my favorite shopping destination in Paris. In fact it reminds me a lot of Target, but smaller.
Great children's department with mix and match collections for your petite fashonistas. The grown-up section isn't bad either -- you'll find fashion forward sweaters, scarves, leather gloves, silk camisoles pretty cheaply. I got a big candy-apple red patent tote here last year.
Their cosmetics section carries the Bourjois line. It's really Chanel but with a lower-priced packaging.
The food department downstairs is not for the casual browser during peak shopping hours. The French love to linger over their meals, but not grocery shopping. They can get quite aggressive as they whip their carts through the narrow aisles.
But if you avoid high-traffic times, you'll find all kinds of wonderful French-made products -- olive oils, canned chestnuts, spices, cookies, candies and more at great prices. Browse at some of the high-priced food boutique epiceries, but buy here. They also have a nice selection of charcouterie, pastries, breads and cheeses for impromptu picnics.
There are locations throughout Paris, but I found the best selection at the Champs Elysees store.