LinkChecker - LinkChecker is a free, GPL licensed website validator.
ServerSuit - ServerSuit is a browser based program that enables remote Linux administration, monitoring, website hosting, and server setup automation.
DRKSpiderJava - DRKSpider is an open source website crawler (sitemap generator) and link checker. Features:
RedGate SQL Monitor - SQL Monitor helps you and your team find issues – before they become problems
Pulno - SEO Audit and Website Analysis. Pull up your SEO.
Netumo - Ensure healthy website performance, uptime, and free from vulnerabilities. Automatic checks for SSL Certificates, domains and monitor issues with your websites all from one console and get instant notifications on any issues.