Office Depot and OfficeMax offers the Smead Monthly Expanding Mini Organizer for $6.49. (Amazon charges the same with free shipping for Prime members.) Opt for in-store pickup to dodge the $9.95 shipping charge. That's the lowest total price we could find by $4. It features 12 pockets with alphabetical and monthly tabs.

Update: It's now longer available for pickup at Office Depot and OfficeMax; however, Amazon still offers it for $6.49 with free shipping for Prime members.