Dr. Link Check - Broken link checker with malware and parked domain detection
Virusdie - All-in-One cloud-based, simple, powerful and gorgeous website security tools built for everyone.
BrokenLinkCheck - Free Broken Link Checker / Online Dead Link Checking Tool - find bad hyperlinks
Sucuri - Website Protection, Malware Removal, and Blacklist Prevention
LinkChecker - LinkChecker is a free, GPL licensed website validator.
Wordfence - Comprehensive security plugin for WordPress.