Hi Alan,
Yes, there are numerous link checking tools out there. Some of the better commercial ones you might want to consider include NetMechanic's
HTML Toolbox and Elsop's
LinkScan. Pricing for these tools is based on the size of your site (i.e., the number of pages in your site to be scanned).
But you don't necessarily have to go the paying route for a link checker, as I recommend you first try some of the free tools out there. A good one is
Xenu's Link Sleuth (which is also available from
TechSoup's Free Downloads section) and there are also free online link-checking services such as
W3C Link Checker.
Hope this helps.
Yann