Finding link partners can take a lot of digging and evaluating.  But here are a few tools and tips that might help.

Link Development Tool - is a very simple search tool that uses an advanced Google search.  It will help you locate a possible link exchange partner based on the keywords you enter.   You might find a lot of things here that you don't want to use (ie., sites that only want reciprocal linking, or sites that charge you to get listed), but it might help you uncover some ideas in just a few minutes.