I haven't uploaded any officially as yet of course, but here is the new version of my "Temp Marker" plugin which is a trivial one.
You can't install it without running from source and winding down the minimum_calibre_version (until 0.7.53 is released) but you can look through the code and compare with my original version which you can download from here
I have a "Foo Example" plugin that I do some find/replace operations on as a starting point for each migration or new plugin that I write. The common_utils.py is a linked file that I share across my plugins containing common utility functions or UI stuff I reuse. I also have a batch file that I double-click on in Eclipse which builds the whole zip and runs it in Calibre, it looks like this for this plugin:
SET ZIPNAME=Temp Marker
wzzip.exe -u -e0 "%ZIPNAME%.zip" ..\_CommonUtils\common_utils.py
wzzip.exe -u -e0 "%ZIPNAME%.zip" *.py
wzzip.exe -u -e0 "%ZIPNAME%.zip" *.txt
wzzip.exe -u -e0 -P -r "%ZIPNAME%.zip" images
calibre-customize -a "%ZIPNAME%.zip"
For more complex plugins I split into additional code files, like a "dialogs.py" for any gui dialogs launched from the InterfaceAction. You will see it is almost identical to Kovid's example (except I put my InterfaceAction class in an "action.py" rather than "ui.py"). Being a rank amateur Python developer myself I am not averse to trying to copy from people who know what they are doing