Meritline offers the refurbished Logitech M570 Wireless Trackball, model no. 910-001799, for $39.99. Coupon code "MLCKBM21L1" cuts it to $29.99. With free shipping, that's tied with our March mention and $8 under the lowest total price we could find for a refurb elsewhere. Features include programmable buttons, USB 2.0 receiver, 2.4GHz wireless, and up to 18 months of battery life. Coupon expires May 22 or after 100 uses.

Note: No warranty information is provided.