Top 6 products relevant to Todos, Note Taking, and File Manager

With Leap you find things based on your natural memory of that file.

Assist in organizing your piles of documents, resulting from scanners, e-mails and other sources with miminal effort.

Open Source

The free version allows up to 30 tags.

With miTaggedMarks you organise and access your local bookmarks using tags, instead of the usual hierarchical tree structure. With a new way to handle a large number of tags. Works with nearly any browser.

TagTower - A personal file tagging and document tagging utility.

Punakea is a little app that allows one to apply tags to files on one's computer.