Microsoft announced today that Cortana is gaining a new skill; the digital assistant can help you to manage you lists for the holiday season. "Whether it’s planning a holiday meal, buying gifts, getting things done before you head out for vacation, or keeping track of who’s naughty or nice, you can use your voice or type to quickly create a new list, add to an existing list when inspiration strikes, and pull up your lists just when you need them on any device."
The feature is exclusive to English speakers in the United States for now, which isn't surprising. It is available on Windows 10 PCs and phones, as well as iOS and Android; however, Microsoft's announcement didn't confirm whether you can use it with Cortana on the Xbox One, although there doesn't seem to be any reason that you couldn't.
For more advanced functionality, Cortana also integrates with Wunderlist (and has for some time). You can sign into your Wunderlist account by going to Cortana's Notebook and then selecting Connected Accounts. Doing this will add features such as the ability to add due dates to a to-do list.