Pulno - SEO Audit and Website Analysis. Pull up your SEO.
Checkbot - Checkbot will boost the SEO, speed and security of your site by checking you're following 50+ web best practices. Browser extension with free and paid plans.
LinkChecker - LinkChecker is a free, GPL licensed website validator.
DRKSpiderJava - DRKSpider is an open source website crawler (sitemap generator) and link checker. Features:
WonderWebWare Sitemap Generator - Sitemap Generator is freeware program that will help you to automatically generate site maps for google, bing and yahoo in their respective file formats.
Dr. Link Check - Broken link checker with malware and parked domain detection