The new advanced application launcher. It is the standard in kde 4.0. It has many features like search, show recently used applications, favorites,...
Classic menu like the one in kde3. It shares the same datamodel with Kickoff and allows to switch between different menu-views.
Lancelot is an application launcher menu designed to provide a place from which all your jobs begin. It provides quick access to applications, places, documents, contacts and system information.
Moon phase applet.
A simple analog clock.
A binary clock.
A simple digital clock.
A fuzzy clock.
A train clock where the numbers flip.
Watch a file on disk.
A trash can applet.
Play the game fifteen puzzle. You can play the game with a custom picture.
Conway's Game of Life applet (more info here
Display the conference group photo.
Get the color value of any color on the desktop.
Show comics on your desktop. This currently supports comics like: Userfriendly, Dilbert, Garfield, Snoopy, xkcd, OsNews Focus Shift.
A picture applet. It can show a single picture or a slideshow of pictures. You can drop an image to show an image, or drop a folder to start a slideshow of the images in the folder.
A dictionary applet. Search the definition of a word.
A applet to encrypt your text using the Rot13 encryption. (more info here)
Shows a 3D model of the earth
A very basic calculator applet.
Monitor your downloads. This applet can show a bar chart, a pie chart and a speed graph.
Amarok moodbar applet.
Monitor down- and upload statistics of your MLDonkey core.
Integrate the tons of existing Karamba Themes as good as possible into the KDE4 plasma desktop.
Lancelot Part makes it possible to add parts of the Lancelot menu directly onto the desktop or panel.
Shows commit log for a project
This week in KDEThe English Breakfast Network (EBN) is dedicated to the contemplation of tea, KDE API Documentation Validation, User Documentation Validation, Source Code Checking, omphaloskepsis, and star-gazing. 
Shows news from various sources
Scrolling feed applet.
An applet to follow people microblogs and microblog yourself using twitter.
Show the current state of the battery. On hover show percentage of current battery left.
This is a modification of the original battery plasmoid of plasma desktop. It displays the remaining battery time.
This is a modification of the original battery plasmoid of plasma desktop. It allows interpolation between battery states which effectivly provides a continuous bar instead of only 6 fill states.
A hard disk usage monitor.
Show hardware info.
Lock the screen or log the current user out.
Shows the recently plugged in devices and notifies the user if a new device is plugged in.
System monitor applet.
A pager applet that shows the virtual desktops.
A system tray applet.
Shows the open applications.