If your looking for Filters right now Home Depot has 3M Filtrete Filters at up to 60% Off!
I just grabbed Filtrete 20 in. x 20 in. x 1 in. Household Dust Reduction FPR 5 Air Filter (2-Packs, Case of 6) for only $23.86 (Retail $59.64).
For more bargains check out the Retail Deals Page!