Needed to renew my antivirus and found that SaveonIT are doing a good price for ESET Internet Security 3 PCs 1 Year (emailed key only, no physical box).
$8.80 if paying by Direct Deposit (+$0.18 surcharge if paying by credit card or Paypal. The usual SaveonIT price for this tends to fluctuate between $10-16, but this is the lowest I've seen in a while. The normal street price is around $12 (e.g. from MSY).
If you prefer Kaspersky they have 3 PCs x 2 years Internet Security for $16.49 (plus extra 2% for CC/Paypal charges).
I have bought keys from these guys for the last three years and had no issues with validity or speed of delivery.