There are many sites in which individuals can purchase unusual Christmas cards. The first place would be Hallmark where they have regular christmas cards but they also offer unusual cards as well.
One can purchase nautical Christmas cards from Paper Cards and Cape Annie's Lighthouse websites. Alternatively one could buy them from Zazzle or Cafe Press, as well as marine charities.
One can purchase tropical Christmas Cards from various online websites such as Amazon or other card selling website. One could also go buy some at a nearby store.
Funny Christmas greeting cards can be purchased at your local stationary store, such as Hallmark. They can also be ordered online from websites like Amazon.
One could take a class at the neighborhood public library on how to make Christmas cards. Some hobby shops might also have kits available for making Christmas cards. Martha Stewart has a website which details how to make Christmas cards.
There are several places that one can buy designer Christmas cards. Online retailers include Amazon and Paper Style. Retailers that offer both online and in store purchase options include Nordstrom and Neiman Marcus.
Vista Print offer personalized holiday cards for Christmas, thanksgiving and other holidays. Other companies one could purchase personalized holiday cards from include Funky Pigeon and Moonpig.
There are many places where one can find Christmas cards online. One can find Christmas cards online at popular on the web sources such as Hallmark and Vista Print.
One could go to a store and look at store cards (Hallmark, or generic cards), and derive inspiration from them. Also, computer software exists that makes cards, so one could be inspired by that. Finally, D.I.Y websites could give ideas for making Christmas cards.
Christmas envelopes can be purchased online or in person. Depending on the level of uniqueness desired, one could get cards from the Etsy market for a highly personalized card. When short on time, any big box store, or pharmacy will have an aisle dedicated to more generic Christmas Cards that can be reviewed in person.
To purchase birthday cards online one could visit the Hallmark site and browse their large selection. One could also find them at Card Store, American Greetings and Cards Direct.
One could purchase Christmas lights that change with music by going to the Christmas Radiance website. The website offers a selection of lights that change to music.
There are many museums that feature the history of Christmas, and most of them likely feature a section dedicated to Christmas cards. You could check out the National Museum of Christmas, Heritage Christmas, or the Canadian Museum of Civilization. You also might want to consider reading "A Brief History of Christmas Cards".