There are two popular choices here. Evolution from Novel and the Kontact from KDE. Both these an email client, calendaring, meeting scheduling, a task list, contact management and syncing functionality. Kontact is essentially the regular KDE PIM components which have been put in together i.e. kmail, korganizer, knotes etc.. It is very a very neat package and is stable and light. Both these are very functional and can connect to many groupware servers.
Klipper is the KDE clipboard utility. It stores clipboard history, and allows you to link clipboard contents to application actions. Klipper can perform actions on the contents of the clipboard, based on whether they match a particular regular expression. For example, any clipboard contents starting with ?http://??can be passed to the web-browser as URLs to open.
Copying text is as simple as highlighting the text. And to paste the text all one needs to do is click on the center mouse button. This can be particularly useful for sys-admins as they use a sequence of commands from time to time. Having these in the clipboard and using them often can make the work a lot easier.
Gaim / Kopete
Communicating via an instant messenger is an essential these days. Linux has a very clean solution for this. Both Kopete (http://kopete.kde.org) and Gaim (http://gaim.sourceforge.net/) are capable of handling multiple IM protocols such as supporting AIM, ICQ, MSN, Yahoo, Jabber, IRC, Novell GroupWise Messenger, Lotus SameTime. Gaim is a multi-protocol instant messaging (IM) client for Linux, BSD, MacOS X, and Windows. It is compatible with AIM and ICQ (Oscar protocol), MSN Messenger, Yahoo!, IRC, Jabber, Gadu-Gadu, SILC, GroupWise Messenger, and Zephyr networks.
KJots is a small program that helps you to write down some short notes and organizes them for you. It has two basic items used to organize your notes - ?Books??and ?Pages?? This is a good light tool to write in all the templated responses and other important notes for quick references.
A lovely password manager which can store passwords for all the logins including those of kopete and websites.