Hamachi is 100% free for non-commercial use with up to 16 clients. Perfect for gamers and home networking.

It also offers SMTP/IMAP Roundtrip-Email Monitoring and VMware Monitoring, Toplists for Packet Sniffing and Netflow Sensors, as well as sensor aggregation using its built-in Sensor Factory.

PRTG Network Monitor includes more than 40 sensor types for all common network services (e.g. PING, HTTP, SMTP, POP3, FTP, etc.), allowing users to monitor networks for availability, speed and failures. As soon as an outage occurs, alerts are sent via email, SMS, pager messages and other means. Request times and downtimes are recorded in an internal database, making it easy to compile performance, downtime and SLA reports. Monitoring, reporting and notifications can be automatically scheduled at specific times. Network maps can be created which provide users with a unique visual network management tool.

PRTG Network Monitor´s Freeware Edition is completely free for personal and commercial use. The Commercial Editions are required if you want to monitor more than ten sensors.

This utility allows you to easily turn on one or more computers remotely by sending Wake-on-LAN (WOL) packet to the remote computers.
When your computers are turned on, WakeMeOnLan allows you to scan your network, and collect the MAC addresses of all your computers, and save the computers list into a file. Later, when your computers are turned off or in standby mode, you can use the stored computers list to easily choose the computer you want to turn on, and then turn on all these computers with a single click.

WakeMeOnLan also allows you to turn on a computer from command-line, by specifying the computer name, IP address, or the MAC address of the remote network card.