The first small modest step towards writing an Ubuntu One client, if I ever get the inclination to do so:

$ curl --user $UBUNTU_ONE_USER:$UBUNTU_ONE_PASSWORD \
> "https://login.ubuntu.com/api/1.0/authentications?ws.op=authenticate&token_name=Ubuntu%20One%20@%20$HOSTNAME"
{"consumer_secret": "...", "token": "...", "consumer_key": "...", "name": "Ubuntu One @ ...

(See https://one.ubuntu.com/developer/account_admin/issue_tokens/cloud/)