Xenu's Link Sleuth - Xenus Link Sleuth checks Web sites for broken links.
Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
LinkChecker - LinkChecker is a free, GPL licensed website validator.
Uptime Monitor by HetrixTools - Minimize your downtime by being the first to know about it
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
Inline Checkout - Inline is a fully secure All-in-one Checkout, Upsells, Discounts, and Cart Recovery App for eCommerce - Shopify & WooCommerce