For those who missed the $1 sale at Staples, or who need to shop for something specific, here is a 15% off at Staples coupon. It is only valid today and Saturday, 01/30/2010 and is not valid on computer purchases. It is an in-store coupon, not for online purchases.
Homeschool supplies you might consider purchasing for 15% off at Staples: binders and sheet protectors (my favorite way to file projects and notes); pens (I'm always losing those); sketch pads; printer cartridges; and calculators (I think they have a range of math and science calculators). Here is a link to the Staples Calculators online - I expect the range at the store will differ.
You might compare Staples prices before making a trip though, sometimes you can get the same price online, and save yourself the gas and travel time. Locally I find Costco and Target to be economical for the limited range of office supplies they sell - I've found binders and sheet protectors for good prices.
Check the ACT calculators permitted list if that is a consideration.
Compare Texas Instruments calculators at Amazon.com (affiliate link).