Printable coupons:
http://print.coupons.com/couponweb/offers.aspx
http://coupons.smartsource.com/
http://www.redplum.com/
http://coupons.target.com - Target (and some manufacturers') coupons
Deal-of-the-Day sites:
www.groupon.com
www.livingsocial.com
Online shopping points or rewards
http://www.ebates.com
http://www.swagbucks.com
Coupon trackers - Quick ways to find the coupons you need in your inserts or online
http://www.hotcouponworld.com/forums/coupon.php
http://www.thegrocerygame.com/app/couponTracker/#SearchCoupons - Put in your ZIP code first!
Coupon clipping services - For a nominal fee, get extra coupons for items you need multiples clipped and shipped to you. I have used both of these sites and they are reputable.
http://thecouponclippers.com/
https://www.couponsthingsbydede.com