Use Nifty Box to keep track of important files and folders on your Mac.

Free Downloads (by the way, Leap does the same thing as Nifty Box, but costs 60 dollars)
Nifty Box Download/
OpenMeta Exporter DownloadUPDATE: OpenMeta Exporter is no longer needed.

Step 1: Create an AppleScript droplet for adding Nifty Box tags to files easily.
on open (the_Droppings)
set theTags to text returned of (display dialog "Pick a tag! (you can add more than one tag by leaving a space between each word" default answer "")
if theTags is equal to "" then
display dialog "You must enter a tag"
exit repeat
else
set defaulDelims to AppleScript's text item delimiters
set AppleScript's text item delimiters to " "
set thelistofTags to text items of theTags
set AppleScript's text item delimiters to defaulDelims
tell application "Nifty Box"
set theFile to the_Droppings
set x to add path POSIX path of theFile
x add tags named thelistofTags
tags of x
end tell
end if
end open

Step 2: Add the Droplet to your Finder Window and drag files to it.

Step 3: Add some tags.

Step 4: This is the result in Nifty Box.

Step 5: Use Spotlight to find files using Nifty Box meta tags (Convert meta tags from Nifty Box to OpenMeta with the OpenMeta Exporter). UPDATE: The newer version of Nifty Box will auto export to Spotlight wihtout the need for OpenMeta Exporter. Tags even show up in the Finder>More Info window.