Don't have one for Christmas cards specifically or anything holiday themed (other than screensavers) but I use the following on iPhone for my Christmas shopping:
1. Grocery IQ -- probably my most used app. I keep all my lists in there: grocery, online orders, books to read, movies to watch, travel supplies to get, emergency prep items to stock up on, ..... maybe Christmas cards I have received??
2. Red Laser - for comparison shopping
3. Game Stop - for game reviews before I buy them
4. Mall Maps - so I can get through malls fast.
5. Evernote - I take a photo of things I'm considering, along with its price tag/label.
Primary Christmas lists I keep in Excel and have it backed up.