Searching with find
Example: find all jpg images from this location and copy them to another location - and don't change permissions or timestamps.
find . -iname '*.jpg' -exec cp -p {} ~/Desktop/test/ \;
and
find . -iname '*.php' -exec chmod 700 {} \;
which will find all php files from here and change permissions on them to conform to the whole suPHP thing (only user-readable php files etc.)

Another one:
find . -type l -name '*.png' -exec mv {} ~/Desktop/crap/ \;
will find all of the symlink-ed png files and move them somewhere

One that matches all text files on the entire system (that is, searching recursively from /) over 10KB, owned by paul, that are not readable by other users, and then use chmod to enable reading, like this:

find / -name "*.txt" -size +10k -user paul -not -perm +o=r -exec chmod o+r {} \;

Find all recently modified files:
find . -type f -printf '%TY-%Tm-%Td %TT %p\n' | sort

NOTE: When typing -exec parameters, be sure to include a space before \;. Otherwise, you might see an error such as missing argument to ´-exec'.