We’ve just introduced a feature that allows you to resize your Linode from one plan to another with the press of a button. Now you can upgrade or downgrade a Linode without requiring a support ticket or waiting on us.
You choose the plan, your account is invoiced (or credited) based on the difference in cost and the number of days left on your billing cycle, and then your Linode is migrated to its new host server. Simple.
Resizes are supported in the API via the new linode.resize() method.