New Reader Lists are not currently available but you can still edit existing ones.
Reader Lists allow you to create and follow lists of blogs and topics inside your WordPress.com Reader. It’s a handy way to bundle groups of blogs into topics you love. You can browse your lists for your own reading pleasure, or share them with the world for others to discover. Please note that all lists are public to all logged-in WordPress.com users.
Existing Reader Lists can be found in the sidebar of your Reader:
Type the name of a list and hit enter:
Now you are editing your list. You can add an optional list description and then add items to your list. Those items can be topics. You can also add individual blogs to your list by entering a URL (any site with an RSS feed will work):
You can click on it to view the most recent content in the list. When viewing a list, you can also copy its URL and share it with the world — it’ll allow anyone to view and enjoy your list:
If you are looking at somebody else’s list and you like it, you can click “follow” next to the list’s title to add it to your own reader: