Update September 21:
After all, I found some time to reimplement the algorithm for highlighting XML. It is now triggered by a new button in the toolbar. As it now does not run automatically, this will be another improvement to overall speed. Feel free to download the new version at the provided download link below or at github!
Update May 5:
Count results are now being displayed in the Status Bar instead of an alert window. Also, there were a couple of bug fixes. Feel free to download the new version at the provided download link below or at github!
Lately I was looking for a small but missing feature in gedit: I needed to be able to count all occurrances of a selected word. This is a standard feature in many other editors such as Notepad++ in the Windows world, for example. However, I didn’t come across a solution on the net, so I decided to write a little plug-in myself.
What it does: After marking a word the plug-in counts all occurrances of the selection in the current document. It adds a new button to the toolbar and an entry to the menu right in the “Search” section. On top of that you may trigger counting the selection by hitting “CTRL+SHIFT+F”. A small pop-up window will appear and show the results of the search. The results will be displayed in the status bar of the window.
How to use it: Simply mark a word, and have a look at the statusbar: The number of search results will be displayed there.

If you find it useful, feel free to download the plug-in here:
Donwload at github:
http://github.com/mmuell23/mmuell23
git clone http://github.com/mmuell23/mmuell23.git
cp -r mmuell23/gedittools/* ~/.gnome2/gedit/plugins