eekboard is a virtual keyboard (aka on-screen keyboard) software package, designed to be flexible and easy to use. For users, it provides a simple program called "eekboard" which works just like other virtual keyboards, though maybe it looks fancier. For developers, it provides a D-Bus protocol server and libraries to access. This allows developers to create custom clients which interact with other desktop technologies such as input methods, desktop keyboard settings, and accessibility.
On Fedora 15 or later, try:
$ sudo yum install eekboard
$ eekboard $ eekboard -f # follow focus changes like other a11y on-screen keyboards
A typical use-case of eekboard is running it on tablet PC. Here is TabletGuide.