-Have flowers delivered to your valentine's door.
-Go out to dinner or a concert: after all, what's more special than spending time with that person?
-Do something random: leave a little note with a poem somewhere obvious, give a phone call telling them you love them, or even try singing a song.
Sometimes the thought means so much more than the money ;)
For those who don't have a valentine, hang out with your friends or do something fun - it's usually hard being alone on Feb.14, so set aside some time to do something you want to do.