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Duolingo, the language learning website, has one currently in beta. The course will be rather brief due to its newness, but if it's like the English course it should cover most of the essentials. They have both a website and a phone application.
A very good place if not THE BEST is lernu.net.
You'll find adaptations of courses like Ana Pana to complete them fully online with a teacher who corrects your exercises and who will help you with any doubts you might have all FOR FREE. From beginner to advanced!