Two small commands with huge possibilities:

1. mdls 

   usage: mdls [-name attr] [-raw [-nullMarker markerString]] [-plist file] path
   list the values of one or all the attributes of the specified file
    -raw: don't print attribute names before values
    -nullMarker: substitute this string for null attributes in raw mode
    -plist: output attributes in XML format to file. Use - to write to stdout
    option -plist is incompatible with options -raw, -nullMarker, and -name
   example: mdls ~/Pictures/Birthday.jpg
   example: mdls -name Keyword ~/Pictures/Birthday.jpg

2. mdfind

   Usage: mdfind [-live] [-count] [-onlyin directory] [-name fileName | -s smartFolderName | query]
   list the files matching the query
   query can be an expression or a sequence of words
   
   	-live             Query should stay active
   	-count            Query only reports matching items count
   	-onlyin <dir>     Search only within given directory
   	-name <name>      Search on file name only
   	-s <name>         Show contents of smart folder <name>
   	-0                Use NUL (``\0'') as a path separator, for use with xargs -0.
   
   example:  mdfind image
   example:  mdfind -onlyin ~ image
   example:  mdfind -name stdlib.h
   example:  mdfind "kMDItemAuthor == '*MyFavoriteAuthor*'"
   example:  mdfind -live MyFavoriteAuthor