Writer's Fallout Shelter

Invest in some cheap, single-subject notebooks. Create one notebook for all the ideas related to shorter works -- short stories and articles -- and a separate notebook for longer works -- novels and other book-length projects. Whenever you get an idea, or a thought about an existing project, jot down notes in the appropriate notebook. That way, they'll be there, waiting, beginning to be fleshed out, when you have time to work on them. In the meantime, select a project (or two) and work on them, leaving the others until they're next up in the queue.