Related content with Tags or textual descriptions

I have 10,000+ contents on my website, all of which are tagged with
acts_as_taggable. Each content also has its own textual description.

When viewing a content, how can I bring up other related content –
sorted by similarity using tags and etc?

Is there an upgrade to acts_as_taggable that would do this?

Or, is this something I would have to write myself?

Thank you,