Tagpad

Tagpad lets you add -- and follow -- hashtags in your own notes. Working on any plain-text document, it features an auto-completer to ease the insertion of tags, and multiple ‘tracker’ windows which let you ‘follow’ your tags and quickly jump to them. For example, you can mark lines with tags such as #todo, #james, #suggestion, #idea, #bug, or #important; and then follow ‘#todo and #important’ for a filtered view of matching lines.