Allow user to subscribe to channels and/or categories

What I’m trying to do is allow a user to specify topics of interest when they sign up to the site, eg: Finance, Automotive, Tax, Offshore etc.

Then they will only be shown posts that have that particular category (or from within that channel if that’s easier)

Anyone done anything similar to this?

I know I can’t natively use checkboxes as custom member fields, but the “Zoo Visitor” tag seems to perhaps offer this functionality, which seems to be the ideal way of allowing users to subscribe to particular topics.

Maybe i’m trying to get EE to do too much, but can’t help feeling this is something that must have been done before.

Thanks