1. Eraser

Eraser is an advanced security tool (for Windows), which allows you to completely remove sensitive data from your hard drive by overwriting it several times with carefully selected patterns. Works with Windows 95, 98, ME, NT, 2000, XP and DOS. Eraser is Free software and its source code is released under GNU General Public License.

An excellent tool for keeping your data really safe, if you’ve deleted it..make sure it’s really gone, you don’t want it hanging around to bite you in the ass.
Get Eraser Here

2. PuTTY

PuTTY is a free implementation of Telnet and SSH for Win32 and Unix platforms, along with an xterm terminal emulator. A must have for any h4×0r wanting to telnet or SSH from Windows without having to use the crappy default MS command line clients.
Get PuTTY Here

3. LCP

Main purpose of LCP program is user account passwords auditing and recovery in Windows NT/2000/XP/2003. Accounts information import, Passwords recovery, Brute force session distribution, Hashes computing.

A good free alternative to L0phtcrack.

LCP was briefly mentioned in our well read Rainbow Tables and RainbowCrack article
Get LCP Here

4. Cain and Abel

My personal favourite for password cracking of any kind.

Cain & Abel is a password recovery tool for Microsoft Operating Systems. It allows easy recovery of various kind of passwords by sniffing the network, cracking encrypted passwords using Dictionary, Brute-Force and Cryptanalysis attacks, recording VoIP conversations, decoding scrambled passwords, revealing password boxes, uncovering cached passwords and analyzing routing protocols. The program does not exploit any software vulnerabilities or bugs that could not be fixed with little effort.
Get Cain and Abel Here

5. Kismet

Kismet is an 802.11 layer2 wireless network detector, sniffer, and intrusion detection system. Kismet will work with any wireless card which supports raw monitoring (rfmon) mode, and can sniff 802.11b, 802.11a, and 802.11g traffic.

A good wireless tool as long as your card supports rfmon (look for an orinocco gold).
Get Kismet Here

6. NetStumbler

Yes a decent wireless tool for Windows! Sadly not as powerful as it’s Linux counterparts, but it’s easy to use and has a nice interface, good for the basics of war-driving.

NetStumbler is a tool for Windows that allows you to detect Wireless Local Area Networks (WLANs) using 802.11b, 802.11a and 802.11g. It has many uses:

Verify that your network is set up the way you intended.
Find locations with poor coverage in your WLAN.
Detect other networks that may be causing interference on your network.
Detect unauthorized “rogue” access points in your workplace.
Help aim directional antennas for long-haul WLAN links.
Use it recreationally for WarDriving.
Get NetStumbler Here

7. hping

To finish off, something a little more advanced if you want to test your TCP/IP packet monkey skills.

hping is a command-line oriented TCP/IP packet assembler/analyzer. The interface is inspired to the ping unix command, but hping isn’t only able to send ICMP echo requests. It supports TCP, UDP, ICMP and RAW-IP protocols, has a traceroute mode, the ability to send files between a covered channel, and many other features.
Get hping Here