1)   IsItUp Network Monitor 6.39
IsItUp Network Monitor is a server, website, port, and email system monitor. It monitors multiple IP devices, websites, servers and ports with alerts via email or pager; graphs. Web content check; performance stats and error log, runs as a service.

 2)   Radar Website Monitor 4.6.1.7
Radar Website Monitor is a multithreaded website monitoring tool, watching different protocols, including HTTP(S), SMTP, POP3, FTP, TCP. It can log the server performance, generate real-time reports, and notify you upon detection of problem or error.

 3)   ServerRadar Server Monitor 5.1.1.3
ServerRadar is a powerful and easy to use website monitoring software. It can monitoring your website, mail server, ftp server, Database server and DNS server. Immediate notification in the event of server errors and HTML reports are also available.