1)   ISAPI_Rewrite 3.1
ISAPI_Rewrite is Apache .htaccess mod_rewrite compatible URL rewriter for Microsoft IIS. It is used for search engine optimization, to reverse proxy another server's content, stoping hotlinking and strengthening server security.

 2)   CustomError 3.0.2
CustomError for IIS allows developers and admins to easily create customized 404 and other default error pages, therefore improving user experience and reducing customer abandonment rates. It can now also redirect any 404 error for SEO optimization!

 3)   httpZip 3.8.4
Port80's httpZip Microsoft IIS Web server software accelerates sites, speeds up Web-based apps, and reduces bandwidth costs dramatically. HTTP compression shrinks the size of common Web files safely and automatically provides browser compatibility.

 4)   CacheRight 3.0.3
CacheRight for Microsoft IIS allows developers to set up granular cache control policies for images and other site content without MMC access. Speed up page loads, reduce network chatter, and ease server strain from unnecessary validation requests.