LinkChecker - LinkChecker is a free, GPL licensed website validator.
Integrity - Feature comparison of link checkers for Mac: Integrity, Integrity Plus and Scrutiny
Dead Link Checker - Check for broken links on any website
Scrutiny - Scrutiny for Mac helps you manage and improve any number of websites. Link check, search, full website spell check, XML sitemap generator, SEO audit
SiteData.co - Website Analysis Tools
Xenu's Link Sleuth - Xenus Link Sleuth checks Web sites for broken links.