Just (almost) interesting stuff!
When your Wi-Fi connection suddenlly drops out or slow down and you dont know why… try the Wi-Spy. It’s a spectrum analyzer on a usb stick. This little thing plugs in your computer and can sense various radio signal. You can use it to sniff around the neighbours radio emmisions. 
Works on USB (1.0 or 2.0) and with Windows 200, XP or Vista.
Ophcrack is a free Windows password cracker based on rainbow tables. It is a very efficient implementation of rainbow tables done by the inventors of the method. It comes with a Graphical User Interface and runs on multiple platforms.
The Open Port Check Tool is a website where you can enter an port number and the site show you if your firewall (or your ISP) is blocking the port!
With this knowledge, you can start serving pages, game servers, remote desktop, etc without trouble!
Just take care not opening too many ports in yout system… 
Wireshark is a great software. Works well and its free!
From the Wireshark page:
Wireshark® is the world’s most popular network protocol analyzer. It has a rich and powerful feature set and runs on most computing platforms including Windows, OS X, Linux, and UNIX. Network professionals, security experts, developers, and educators around the world use it regularly. It is freely available as open source, and is released under the GNU General Public License version 2.Features
Wireshark has a rich feature set which includes the following:
