Page-links-to Plugin - could link to ads on other sites
http://txfx.net/code/wordpress/page-links-to/
If I understand this plugin correctly, it lets you redirect posts and pages to any URL you choose.
An admin of a classifieds site could use this to make posts that link to ads on other websites. Might be useful starting out so your site doesn't look empty, only prob is you're sending people away from your site, but maybe that's ok if your site has some appeal.
