If some of the arrangements you have made with link partners include reciprocal linking, how can you monitor them?  Here's a nifty free reciprocal link checker.

This free reciprocal link checking tool allows you to monitor if link partners are still linking back at your site. 

While we can't vouch for its guaranteed accuracy, we've found it to be fairly accurate in our tests.  (Important note: if this tool indicates a site is no longer linking back to you, it might be wise to manually check the partner's site before you contact them and ask "where is my link?"  Most sites go through site platform reorganization or change staff, and many times search engines don't accurately report back links, so it's always good to approach this gently, and not rely solely on software tools to make conclusions).