coupons.com and click on "health care" on the left hand side, or keep browsing until you see the ad on the right hand side for free Excedrin. You should be able to request one for Excedrin Extra Strength as well as one for Excedrin Migraine. There is also a high value coupon on the same site for $3 off Excedrin PM that will go great with the deal also. Unfortunately, I doubt if you request the coupons now if you will get them by the end of the sale:( But you can still get some free Excedrin!! :)
**Update** There is also a $1 off Excedrin coupon at redplum.com Remember that the coupons will reset on the first of January...so print now if you want to use these!