Naturally the first recommendation is MyCouponspot. Coupons for $200 in your choice of groceries, and if your grocery store does double or triple coupons, you can save even more!
These free sites offer online coupons which are generally for things like electronics and online shopping.
Deals such as a certain % off an order at amazon.com or Staples if you spend 50 or a hundred dollars.
CoolSavings has banners up everywhere so you may have seen their ads. Link
mycoupons.com has forums. Link
Coupon Mountain Link
The Yahoo Coupon Directory Link
Slick Deals Link
And check out free.com for (admittedly mostly not grocery related freebiesLink