The new target story in Eclipse 3.5 allows you to have multiple targets in your workspace. With this one really needs a means to see what constitutes the active target definition. For this reason, we now have a new view - Target Platform State (I don't like to call it TPS view :-)). It can be found in Window -> Show View -> Other... -> Plug-in Development -> Target Platform State.
This is how it looks like
Target Platform State view
What is it good for?
The target platform state view displays the bundles selected by the active target definition. And also their version and the location they are getting picked from. Thus, if you are facing an issue such as plug-in dependency not getting resolved as expected or wrong version of the plug-in getting picked up, the target platform state is where you should be looking.
It also displays, for each plug-in, the required plug-ins and the packages it imports and from where.
Required Plug-ins and Imported Packages
The view is a filtered one.
view filtered for org.eclipse.pde.ui
And when the "Show only unresolved plug-ins" menu choice from the view menu is used, the view only those plug-ins are shown whose dependencies can not be resolved. With all dependencies resolved this one should show a blank view. The "Show leaf plug-ins" will show only those plug-ins on whom no other plug-in depends. They are the leaf of the dependency tree.
Target with only Mylyn plug-ins without Eclipse SDK