Old Navy Weekly

For those of you Old Navy shoppers that don't know already....
You need to check out www.oldnavyweekly.com for fabulous deals. I've been told to check it on Thursday or early Friday mornings for the best deals. They sometimes have "$75 off your purchase of $100 or more." I know a lot of you know about it already but I had to share, just in case.

What's the "Deal" with Coupons?

I have run into some coupon websites recently and I have been honestly amazed at some of the extreme deals to be had. Free toothpaste, 50 cent mouthwash, and $60 in groceries for 33 cents? This is crazy! The idea is intriguing to me but here is my problem. I don't have any idea what most of the websites are talking about. They have their own little lingo and I don't know what it means. For example: "04/26 RP $3.00/2" or "Use TWO $1/1 from 5/3 P&G".
Does anyone know of a place beginners can go to learn the lingo?
Also, anyone recommend some good coupon sites?
I was also wondering if anyone who is into this can tell us if it is worth it? Do you really save enough money on the stuff you need to make it worth the time and effort? Do you buy a ton of stuff you wouldn't have otherwise spent money on because it is such a good deal?