Network Toolkit

Ping
Ping will do exactly that and defaults to the client IP. The server's own latency is about 25ms.

Probe
Probe will check if a port on a remote host is open and connectable. If the port is not 80, the probe will then close the connection. If the port is 80, the probe will send a HTTP/1.0 HEAD request and output any response. This can be used to check if your torrent client is correctly configured, for example.
There are three possible results:
Connection refused - The target machine responded, but refused the connection as the port is closed.
Connection succeeded - The connection was successfully made and the port is open.
Connection timed out - A connection attempt was made, but no response arrived.

Trace
Simply traces the route from this server to any other host, defaults to the client IP. This may take a long time to run and no output is given until the entire trace is complete.

Link
Checks if a website is online. Useful for answering "is it down or is it just me?"

DNS Lookup
Simply performs a DNS lookup (e.g. GetHostByName). Does not support reverse DNS.