Product "to-do" lists
tonyarkles: At the last startup I worked at, we used Jira [http://www.atlassian.com/software/jira/] as an issue tracker.  As ideas came up, we had a separate category for "idea issues".  This kept everything in the same place, so when we wanted to work on a feature that was previously a TODO idea, we'd just assign it to someone to work on.  Because it had been kept in JIRA for its entire lifetime, all thoughts and comments that people had had about it were already there for the implementer to consider.