Adding to Mac OS X contextual menu Templates like on Linux Ubuntu

Does there exist some method to add the Create document function to the context menu? I would love a function like this with the Templates folder because I always need to create files with the same template inside and place it in different folders.

Does there exist some app to do this or some Context menu modification for Leopard or Lion?

There are a number of ways you could do this.

1. You could use Automator to create new documents through a Service:
   http://pauloppenheim.wordpress.com/2011/06/03/mac-finder-add-new-file-context-menu-item-open-source/

2. Use a context menu plugin, but these are less common on 10.6 and 10.7. You may need to run them using Shortcuts:
   http://www.abracode.com/free/cmworkshop/macosx_10_6_snow_leopard_and_contextual_menu_plugins.html

3. Best of all, in my opinion, you can use a little known OS X feature called Stationary Pad. It's on the Get Info dialog of any file. The way you would go about using it is to create your template file, mark it as a Stationary Pad and then every time you double click it a new copy of that template will be created. Read more:
   http://ignorethecode.net/blog/2009/05/31/creating-new-documents/

Not sure if I understand your question correctly. If you want to create new files from some template(s), there's no need for a context menu entry. Just mark the template file as "Stationery pad" by opening the file's Info window in Finder (⌘i or menu File > Get Info) and selecting "Stationery pad" in the "General" section.

Then, double-clicking that template file will always make a copy of it and open the copy using the default application. You just save the copy under a different name wherever you need it, and your template stays where it was.