I see that iCloud can create groups. It appears that other than All Contacts, I only have another group, contacts-other that was created when I imported my addresses (I think via Outlook, which I no longer use).
How can I assign contacts to a group? Either on the phone or icloud.com would be fine. Since we have a mixed Mac/Windows environment, I would prefer to avoid OS X-specific solutions.
EDIT: It would also be nice to know which contacts aren't in a group other than All Contacts (or ideally contacts-other).