I beleive many free forum sites let you restrict users to certain areas. As for normal "member areas," that sounds like one of those features free hosts like to dangle in your face to try and make you pay, so I wouln't cont on finding a free one easily.
If you are serious about your site though, I would suggest you check out one of the more reputable payed hosting companies. You could probably find a decent deal with PHP (for forums/site makers like e107) and a mysql db for around $5-10 monthly.