I guess many of us were waiting for this: the possibility to use Sigma's excellent…
Buy 1 pack Canon Glossy Photo Paper 4×6 at $10, get 9 packs for free (500 sheets)
The Canon Store has a ridicolous deal on Canon Glossy Photo Paper – GP-701 – 4×6. Buy one 50 sheets pack at $9.99 and get nine more 50 sheets pack for free, for a total of 500 sheets.