Test your maximum upload speed and download speed from several geographically distributed locations. Java, Flash and iPhone speed test (100% browser) available.
Free Network Diagnostic Tool. WinMTR is an equivalent of mtr for Windows.
The program is no longer updated. Last version, 0.92, released in February 2011, can be still downloaded from the official website.
UptimeLine makes a request to your website every minute to check that it is responding.