The Internet is what most use computers for more than anything else I feel. Sure I still use plenty of other software, but at least half of my computing time is devoted to the Internet nowadays. Here is the software I use on a daily to weekly basis. Most of it is Linux software, but I also mention Unix CLI and Windows programs I use, have used, or recommend for some things.

• BitTorrent: KTorrent - BitTorrent is a great network for downloading larger files. In my case this is mostly the ISO's of Linux distributions. KTorrent is my preferred torrent client. I have never really used BitTorrent before switching to Linux, but I generally recommend Azerus to Windows users based on its Linux version. rTorrent is the best terminal torrent client I've come across, though I don't usually use BitTorrent in that environment.
• Download Manager: KGet - I had never seriously used a download manager before I started using KGet. For larger HTTP downloads, it is quite useful. I use the FlashGot extension to use KGet with Firefox.
• E-Mail Client: KMail - Honestly, I am not a huge e-mail user. Nonetheless, I can be quick finicky about what I want in a mail client. KMail does what I want in a free mail client and does it well. For people seeking an alternitive to webmail, Outlook Express, or an old version of a commercial mail client, however, I recommend Thunderbird. About everyone I've shown it to seems to be happy with it.
• FTP/SFTP: Dolphin - I generally save directly to FTP/SFTP from KDE applications thanks to KIO slaves. When I do need to manually copy files over, I use my file manager, which is Dolphin. I keep a copy of Filezilla on my jump drive for when I'm on Windows.
• Instant Messenger: Kopete - Kopete is a great multiprotocol instant messenger. I originally switched to it for its webcam support, but have come to love it, especially since I spend a lot of time in it. When on the terminal I use BitlBee (under irssi) and on Windows I go for Pidgin (formelly known as Gaim).
• IRC: irssi is about the only terminal program I use exclusively. irssi, combined with screen on an external shell, is a great program. I recommend Anapnea for using it.
• RSS Reader: Google Reader - Google Reader is the web application I use most. I especially enjoy the single finger shortcuts to browser through my feeds. In fact, my typical Google Reader session is similar to: j/j/j/space/j/j/space/space/space/s/j/j/j/j/k/space/s/j/s/j/j/j… and so on. j advances an item, k goes back an item, space scrolls, and s stars an item.
• Web Browser: Firefox - Firefox is probably the most popular browser, though maybe not most used, browser around. I have my 'fox quite customized and now have trouble using other web browsers I'm so accustomed to how Firefox works. When in the terminal I use elinks, which is very featured for a web browser with no GUI.
• VOIP: Skype - Skype is often criticized for not being open. Unfortunately, this is what everyone I know that uses VOIP uses, so I don't have too much of a choice.

There's my list. I'm interested in how this compares to others. Has anyone else every made a similar list in the past, or willing to make one now? Let me know in the comments.