After niche-specific links, Smarty says to go after your
competitors' deep links--appending the previous search parameter with filters, or using tools to find the most authoritative resources that are linking to the inner pages of their Web site.
Finally, you should explore the targeted anchor text that others use to identify their links to your competitor's site. Smarty suggests the free "link diagnosis" tool (created by Janusz) that offers this kind of filtered, detailed info.