In Sitecore 6 we've added a an information-action panel to the left of the tree. We call it Quick Action Bar.
One of the default examples is that you can see an icon warning you that the item will not be visible on the website, because it's not published.
Quick Action Bar is pluggable, so you can create your own warning that will display an icon if the item doesn't have a version in the current language. You can also add related actions, so that you can click on the icon an maybe create a version right there.
Take a look at Client Configuration Cookbook at SDN for related docs.
It's also possible to change item styles to make item name use italics in tree, but it's not as easily pluggable for dynamic scenarios like yours.