The new advanced application launcher. It is the standard in kde 4.0. It has many features like search, show recently used applications, favorites,...
Traditional menu (like the one in kde3).
A simple analog clock.
A binary clock.
A simple digital clock.
A fuzzy clock.
Watch a file on disk.
Get the color value of any color on the desktop.
Show comics on your desktop. This currently supports comics like: Userfriendly, Dilbert, Garfield, Snoopy, XKDC, 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.
Shows a 3D model of the earth
Monitor your downloads. This applet can show a bar chart, a pie chart and a speed graph.
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. 
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
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.
Play the game fifteen puzzle. You can play the game with a custom picture.
Lancelot - as launching-lot (lot as in parking-lot). The main idea that was guiding me was to create a simple application launcher (and nothing more than that) that would have a no-click (Absolutely No Click Needed At AllTM) interface. You can find more info on the blog of the author Ivan Čukić.
A pager applet that shows the virtual desktops.
A system tray applet.
Shows the open applications.