LinkChecker - LinkChecker is a free, GPL licensed website validator.
SiteCheckerTool.com - Website Analytics & Tools
DRKSpiderJava - DRKSpider is an open source website crawler (sitemap generator) and link checker. Features:
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.
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.
SEO PowerSuite - Get all SEO tools in one pack - download free edition of SEO PowerSuite and get top 10 rankings for your site on Google and other search engines!