Here are sample RUP documents I created for a training I gave:
The requirements set:
The management set:
The most important ones are the vision document and the use cases. One thing I really like about the vision document is the problem statement, defining clearly the problem to be solved by the system.
One important thing I see missing in many “processes” is an explicit focus on finding what the user needs (can be very different of what the user wants), clearly stating the problem to be solved helps a lot in that direction.
Also you need to have some alternatives identified. How many projects are started without a clear problem to solve? Sometimes they're successful, but you must be VERY lucky to pull this off.
Also the alternatives are important: developing good software is very difficult: sometimes, something like excel is good enough!
Basically, it boils down to clearly defining the problem and have the alternatives in mind instead of jumping blindly into a development project.
BTW, the problem statement is not exclusive of RUP, they're just requirements management good practices. Even is included in the IEEE 830 SRS standard.