Xenu's Link Sleuth - Xenus Link Sleuth checks Web sites for broken links.
Dead Link Checker - Check for broken links on any website
LinkChecker - LinkChecker is a free, GPL licensed website validator.
BrokenLinkCheck - Free Broken Link Checker / Online Dead Link Checking Tool - find bad hyperlinks
Integrity - Feature comparison of link checkers for Mac: Integrity, Integrity Plus and Scrutiny
A1 Website Analyzer - Analyze websites and save data into XML, CSV etc. Extract data about internal linking and importance calculations, file sizes, download times, HTML validation errors etc. across entire websites.