Each time you have a new idea, put your notes in a repo for it, instead of simply storing it Dropbox or on your local computer.

If it's an open source project, push that repo to Github. Then you can advertise it on a public repository like Github, and actually start working on it and without having it complete.

This will get you started quicker, and when you have some time or you want to go back to that project, it will be all ready for you.