Both Markdown and Textile have (i think) java implementations (parser/transformer) as well as js editors.
OTOH, we have our wiki rendering module which also provides some of this.

BBCode seems to me a little "hairy", and hard to maintain; i'd rather on an existing library, and something more modern (wiki rendering module might sooner or later move to markdown/textile as well)

http://en.wikipedia.org/wiki/Category:Lightweight_markup_languages