Definitely a fan of RetailMeNot and Groupon.
Some other sites I recommend for online shopping are BeFrugal, Ebates, WikiBuy and Honey.
One specific way you can save money when shopping for such items is to buy discounted gift cards to the stores you are planning on buying from.
It's not a lot but you can sometimes find gift cards that cost anywhere from $2 to $10 less than their actual value.
I frequently use this method to save money when eating out and would use it for any stores I planned on making a purchase at.
Raise.com is my personal favorite for buying discounted gift cards.