How to list all untagged files in Mavericks Finder?
Solution 1:
Ok, I should have taken a look at SuperUser, here's a way to do what AllInOne says without fiddling with XML files (and it's faster).
Simply create a new smart folder or hit cmd+F, choose "Raw Query" from the filters and type kMDItemUserTags != '*' in the field.
Solution 2:
A simple way to do this in Finder...
At the top of the finder window you see the column headers such as "Name", "Size", "Kind" etc like in the picture below.
Just right click on any column header and you can add a column called "tags"as seen here.
Then you can sort that column.