Agency holiday cards have become a big deal. Some clients would be happy to have as much work put into their ad campaigns as some holiday cards receive. Then again, as always, it's usually the quality of the idea that prevails. (Our favorite card this year is almost all idea, with just a tad of execution.) After the jump, check out our picks for the 10 best and five worst agency holiday cards of 2011. We looked at hundreds of these things, though of course we probably missed some. Leave links to yours in the comments.