I am revising some things in my campaign after a hiatus of about a year. Tha last year at work was just... ugly. Massive work overload and no spare time. Yes btw, PRPG figures into it now :) Anyway, I was looking over some of my house rules and ideas and considering changes to them. It occured to me that advice from other players / DMs could be a good idea. Glancing around the boards here, the closest I see to an advice / suggestion forum on this is the Proposed New Rules section of the PRPG Alphas or the General Discussion Forum for D&D 3.5 / d20 / OGL. Not exactly what I was looking for. What about a "housrules / homebrew" forum for the DM. It could have subsections for different areas and people looking for ideas or advice could go to specific sub sections to post or read... of course this could get chaotic and messy... no, make that *would* get chaotic and messy. Still, it could be useful.
I requested something like this a while ago, since the Alpha Forums and presumably the Beta Forum are temporary I was thinking something outside those forums would be good. No luck yet. You could post here: http://paizo.com/paizo/messageboards/community/gaming/dnd which is general OGL content. It's not PRPG specific but it is a permanent board.
If your doing this in PRPG then you should pick one of those forums.
If this is just generic 3.5 then I suggest using the 3.5 forum (it could use some more action these days in any case).
If 4E is your cup of tea then the 4E forum would be the place to post.
A specific House Rule Forum strikes me as a bad idea. We'd actually need three of them, one for PRPG, one for 3.5 and one for 4E) and thats getting kind of excessive. House rule threads can exist amicably beside character idea threads and rule debate threads, IMO.