I use the forums mostly. I hardly ever actually use the site unless I'm really stuck on a quest or something but even then I don't really use the website much.
As for the forums, these are the sections I visit mostly:
Runescape Help boards (for guests and members) this is where most of my time in forums is spent, being a Community Crew member and all
I also sometimes visit the submissions board, but not as much as the ones I mentioned above.