Mozilla Firefox

Mozilla's free, open-source web browser, FireFox, is very popular, and available for a wide variety of platforms. Firefox's extension system allows the user to add any number of add-ons to Firefox, which offer a staggering array of options to block ads, add functionality, enhance security, and much, much more. Thanks to a very large user base, the selection of enhancements is constantly growing and improving, and security issues are addressed very quickly.

Free, open-source, available for many platforms

Opera

Opera is a popular free web browser that offers much more than simple web browsing, and has many unique features and capabilities. Opera offers browsers for many platforms, including phones and other portable devices.

Free, available for many platforms

Google Chrome

Google's Chrome web browser is available for a variety of platforms, and is most often lauded for the speed with which it displays web pages.

Free, based on Google's open-source Chromium, available for many platforms

SRWare Iron

Iron is a free, open-source web browser, based on Google's Chromium, offering all of the benefits of Google Chrome, but with some important differences. Iron is very similar to Chrome, but SRWare removes the usage tracking built into Chrome, and implements various other security and privacy enhancements.

Free, open-source, available for many platforms

Safari

Safari is Apple's web browser, offered for free for a variety of platforms.

Free

Internet Explorer

Internet Explorer is Microsoft's browser, which is typically included with all versions of windows. If you do not yet have Internet Explorer, or if your version is out of date, Microsoft offers it for free download.

Free

Mozilla Thunderbird

Mozilla's free, open-source email and news client, Thunderbird, is very popular, and offers many of the same benefits of extensions and add-ons as their web browser, Firefox. Thunderbird supports a variety of email standards, including Google's Gmail, POP3, IMAP, SMTP, and so on, along with some of their associated, and more secure, implementations. Thunderbird is available for a very wide variety of platforms and operating systems, and supports a large number of enhancements to improve organizing messages, junk filtering, and customizable filters to automatically handle messages.

Free, open-source, available for many platforms

Opera Mail

Opera's free web browser includes an integrated, full-featured email client, and is available for a variety of platforms.

Free, available for many platforms

FileZilla

FileZilla Client is a free, open source FTP client that supports FTP, SFTP, and FTPS, and is available for many platforms, including Windows, Linux and Mac OSX. With a polished user interface, the capability of using secure FTP protocols, large file (greater than 4GB) transfer/resume, and a number of other advanced features, FileZilla has become extremely popular, and is a great solution for any FTP related needs.

FileZilla also offers a full-featured FTP server, FileZilla Server; the vast majority of users will only need FileZilla Client.

Free, open-source, available for many platforms

PuTTY

PuTTY is an open-source, free client for SSH, telnet, and rlogin protocols, allowing connection to a remote system. Most users will never need this type of software, but if you do, PuTTY is a fine choice.

Free, open-source, available for many platforms
Recommended for advanced users

Xming

Xming is a free X Window Server for Windows, that offers a full-featured and secure solution for those that need it. Xming works perfectly with PuTTY, creating a combination that works very well. Like PuTTY, most users will never need this software, but for those that do, PuTTY and Xming are hard to beat at any price, and probably impossible to beat for free.

Free
Recommended for advanced users

Pidgin

Pidgin is a GPL-Licensed, free, open-source instant messaging client that supports almost every popular standard for instant messaging, in one single program. Supported protocols include: AIM, Bonjour, Gadu-Gadu, Google Talk, Groupwise, ICQ, IRC, MSN, MySpaceIM, QQ, SILC, SIMPLE, Sametime, XMPP, Yahoo!, and Zephyr, with more added as they become available. Pidgin can be extended with a variety of add-ons, and with a large user base, the selection is always improving.

Using Pidgin takes a little getting used to, but if you are looking for an all-in-one tool for all of your IM accounts, Pidgin is definitely worth checking out.

Free, open-source, available for many platforms

Skype

Skype allows users to make free voice and video calls to other Skype users, and low-cost calls to landline and mobile phones, over the internet. Skype is a great choice for free PC-to-PC voice and video calling, and low-cost PC-to-Phone voice calling, but keep in mind that it requires a broadband internet connection, it isn't a replacement for your other telephones, and it can not be used to make emergency calls.

Free, available for many platforms

µTorrent

µTorrent, also known as "Microtorrent" or "Mtorrent" is a very popular, lightweight, and full-featured BitTorrent client, supporting bandwidth prioritization, scheduling, RSS auto-downloading, Mainline DHT, the Protocol Encryption joint specification, and peer exchange. The benefits of the legitimate use of BitTorrent are being realized by more and more companies every day, so selecting a quality BitTorrent client is becoming more important, and µTorrent is a fine choice.

Free, available for many platforms

Miro

Miro is a free HD-capable video player, podcast client, and much more, that can play almost any video file and offers thousands of free internet TV shows and video podcasts.

Once you subscribe to your favorite feeds, Miro will check for and download new audio and video webcasts automatically, and organize everything into a clean, easy-to-use interface. Files can be saved forever, or will be automatically deleted after a specified number of days; users can specify how much disk space to allow, so Miro won't fill up your drive unless you want it to. Since Miro actually downloads most files to the local harddrive, they are available while you're on the go and away from an internet connection.

Free, open-source, available for many platforms