There's no general way to do that since HTML doesn't define character entities for all possible characters. If you've specified that utf-8 is in use throughout (database, Rails [Ruby's $KCODE], HTML), then you shouldn't need to convert. Of course, the end user may not be able to see the character you intend if his/her system lacks a suitable font.
-Rob
Rob Biedenharn http://agileconsultingllc.com Rob@AgileConsultingLLC.com