I've created (with lots of help from GuyR and Elizabeth Shulok in this thread: http://forums.augi.com/showthread.php?t=70906) a utility that will find all of the elements that are associated with a certain level.
The reason I created this is to help out with times when you want to delete a level. Revit does not warn you about what is associated with a certain level (and therefore will be deleted when the level is deleted. We have had cases where minor levels were deleted and we found out later that some elements were deleted with the level that we didn't realize were associated.
So, simply run this tool, which will give a list of levels in the project, let you choose one, and then show you all the elements on that level or tell you if there are none. It will also then let you select or select and show the elements.
One caveat is that stacked walls seem to act a little strange. They do not schedule in themselves, but the pieces of them will show up twice; once as a wall and once as a curtain panel. Try it with a simple project with only a single stacked wall and you'll see what I mean. Because of this I have put in a warning if there are stacked walls present telling the user just this. This does not, however, effect the selecting/showing. All elements will be selected still.
I'm very new to programming so go easy if there are bugs, but please let me know and also if you have any ideas for improvements let me know.