I have compiled a list of programs that I use on a day to day basis for general IT administration. (the descriptions below are mostly copied from Wikipedia)
PuTTY is a free and open source terminal emulator application which can act as a client for the SSH, Telnet, rlogin, and raw TCP computing protocols and as a serial console client.
** Step up from PuTTY is SecureCRT but it's not free :(
FileZilla is free and cross-platform FTP software, consisting of FileZilla Client and/or FileZilla Server.
Nmap (Network Mapper) is a security scanner used to discover hosts and services on a computer network, thus creating a "map" of the network. To accomplish its goal, Nmap sends specially crafted packets to the target host and then analyzes the responses.
Wireshark is a free and open-source packet analyzer. It is used for network troubleshooting, analysis, software and communications protocol development, and education.
WinMerge is a free software tool for file comparison and merging text-like files. It is useful for determining what has changed between versions, and then merging changes between versions.
Notepad++ is a text editor and source code editor for Windows. One advantage of Notepad++ over the built-in Windows text editor, Notepad, is tabbed editing, which allows working with multiple open files. And it's Free!
WinSCP (Windows Secure CoPy) is a free and open source SFTP, SCP, and FTP client for Microsoft Windows. Its main function is secure file transfer between a local and a remote computer. Beyond this, WinSCP offers basic file manager and file synchronization functionality. For secure transfers, it uses Secure Shell (SSH) and supports the SCP protocol in addition to SFTP.
Windows Grep is a tool for searching files for text strings that you specify. Although Windows and many other programs have file searching capabilities built-in, none can match the power and versatility of Windows Grep.
Angry IP Scanner (or simply ipscan) is an open-source and cross-platform network scanner designed to be fast and simple to use. It scans IP addresses and ports as well as NetBIOS information (computer name, workgroup name, and currently logged in Windows user), favorite IP address ranges, web server detection, customizable openers, etc.
Cain and Abel is a password recovery tool for Microsoft Windows. It can recover many kinds of passwords using methods such as network packet sniffing, cracking various password hashes by using methods such as dictionary attacks, brute force and cryptanalysis attacks. Cryptanalysis attacks are done via rainbow tables which can be generated with the winrtgen.exe program provided with Cain and Abel.
Microsoft Visio is a 2D-object drawing application. I use this program for drawing all types of diagrams.
Tftpd32 (or Tftpd64) is a free, opensource IPv6 ready application which includes DHCP, TFTP, DNS, SNTP and Syslog servers as well as a TFTP client.
TeamViewer is a proprietary computer software package for remote control, desktop sharing, online meetings, web conferencing and file transfer between computers. The software operates with the Microsoft Windows, OS X,[1][2] Linux,[3] iOS,[4] Android,[5] and Windows RT[6] operating systems. It is possible to access a machine running TeamViewer with a web browser.[7] While the main focus of the application is remote control of computers, collaboration and presentation features are included.
TightVNC is a cross-platform open source remote desktop software application that uses and extends VNC's RFB protocol to control another computer's screen remotely. It was created by Constantin Kaplinsky. His extensions provide for 'tight encoding', which improves performance over low bandwidth connections.
Dynamips is an emulator program that was written to emulate Cisco routers. Dynamips runs on Linux, Mac OS X or Windows and can emulate the hardware of the Cisco series routing platforms by directly booting an actual Cisco IOS software image into the emulator.
KeePass Password Safe is a free software password management utility for Microsoft Windows, with unofficial ports for Linux,Mac OS X, and a variety of other systems.
FrostWire is a free, open source BitTorrent client first released in September 2004, as a fork of LimeWire. It was initially very similar to LimeWire in appearance and functionality, but over time developers added more features, including BitTorrent support. In version 5, Gnutella support was dropped entirely, and FrostWire is only a BitTorrent client
