Where on your forum do you place your links for link exchanges and such? On some forums, I see the links as forum redirects at the very bottom of the forum list (on the index), and others on the sidebar. On my forum, I put links to other sites on the footer of the index page.
I haven't been a fan of placing sitewide links on my sites to other sites for a few years. I've tried to use a box in the side column, and I'll place a few links there. I always try to keep my external links under 20, otherwise you'll end up hurting your own site which none of us want.
