Misc
System Monitor
Gkrellm is a cruel name for a program, but who cares. It shows you the state of your system in several little windows: How much CPU and RAM is used, the traffic of the network and so on. You can extend it with several plugins (e.g. a XMMS-plugin and a wheater-plugin) and you can change the look with themes.
File Manager
Nautilus is GNOME's default file manager. It creates previews of images and videos and can be extended with shell scripts easily. The icons are themeable even SVG-icons can be used.
Terminal Emulation
Though there are a lot of programs that have a GUI, you occasionally need to use the console as well. Running your desktop environment, you must have access to a console and I prefer GNOME terminal. You can open and switch to tabs using shortcuts.
Encryption & Signing
If you don't want the whole world to read your private email, use GnuPG to encrypt and sign them. You may also encrypt and sign normal files to make them useless for unauthorized people to use them. Sylpheed is a great email-client which can utilize GnuPG. You can use GPA as frontend.
Signature Generator
Signify is a very cute program: It generates dynamic signatures (e.g. for email or newsgroups) from a set of defined rules. Each time signify is run, it generates one. You can define several dynamic and static parts and align them.
