Thanks again for your post. We're actually working on a Male and Female section of the area, actually thank you for reminding me.
I'll put that on my list for tonight to do.
When you refer to them being invisible, how would you propose that be done?
When viewing the main list of forums presumably there's some kind of query that goes along the lines of "select f.name, f.description, f.postcount from forum f, forumaccess fa, user u where fa.forum=f.id and fa.user = u.id" (slightly more complex to take account of grouping and sequence but trying to keep it simple here).
You could potentially create user groups where each user can be a member of multiple groups - there will already be groups with names like "administrators", "moderators", "members" etc so if you can be a member of many groups you could also have "men", "women", and groups for however many denominational forums you want to have. Either that or have something along the lines of:
select f.name, f.description, f.postcount from forum where accesstype = 0 union select f.name, f.description, f.postcount where accesstype = 1 and f.accesscode = (my gender) union select f.name, f.description, f.postcount where accesstype = 1 and f.accesscode = (my denomination)
(in this example accesstype would be a field where 0 = open access, 1 = gender specific, 2 = denomination specific. The accesscode field would define who could access it based on accesstype, so for a gender-specific forum you might say male=1 and female=2, for a denomination-specific forum you'd do something similar for denominations.)
Just like when I click on the New Posts I don't see new posts within the moderators-only areas, when I click on the forum list I don't see the moderators-only forums, so the same would apply regarding the women's area and denominational forums that don't match my own denomination. If you wanted to you could hide all the Christian-only forums from anyone who isn't listed as some variation of Christian.