Link Checkers

• Link Checker Pro: Great solution for detection of broken links. Download a trial version. A permanent academic license is $75.
  
  
• Xenu's Link Sleuth: Free, Windows-based link checker with support for SSL-secured sites.
  

Log Analysis and Reporting

• Analog and Report Magic: Analog is the most popular logfile analyser in the world, and for good reason. It's public domain software, very easy to use, and when combined with Report Magic, you get very usable, comprehensive reports of your Web site traffic. Here's a sample report:
  

• Sawmill: Universal log file analysis and reporting software that works with Unix, Linux, Windows, and Macintosh platforms and can be run locally or remotely. Free trial version. Lite, Professional, and Enterprise editions; pricing starts with a single-installation license.
   

Validators

• W3C Markup Validator: Free service that checks Web documents in formats like HTML and XHTML for conformance to W3C Recommendations and other standards.
  
  
• BrowserCam: Screen capture service lets you test the appearance of your Web pages in various browser/OS configurations. Remote access service lets you log in to a remote server to test your Web functionality from various browser/OS configurations. Pricing starts with one-day access.
  
  

Other

• Web Developer: Free, highly-rated Firefox Extension that adds a browser menu and toolbar with useful Web developer tools, including features for CSS, forms, images, document information, outlining, disabling, cookies, and more. Web Developer is designed for Firefox, Flock, Mozilla and Seamonkey, and will run on Windows, Mac OSX, and Linux.
  
  
• Webserver Stress Tool: Test application that simulates any number of users accessing your Web site at the same time, to demonstrate performance capabilities under peak loads. Free, fully functional trial version. Professional and Enterprise editions; pricing starts with a single-user license.