Sure, let's break down your question, and analyze why it was probably down voted.
I have a sales force application(not related to force.com) which I am trying to integrate with the force.com.
What do you mean by a Salesforce application not related to Force.com? What is the nature of this "integration"?
I have organizational hierarchies, user hierarchies and even campaign hierarchies. Now I want to know what options do I have on integrating this functionality into force.com.
How can know we what options you are looking for when we don't know the nature of your integration? or why do you differentiate between a Salesforce application and Force.com? Do you mean a Salesforce org and a seperate Force.com application? Does this application reside on a site, or a seperate org?
I know that I can add an attribute of the same kind of object on an object so that a hierarchy can be maintained but like to know if there is any inbuilt functionality in the force.com that support hierarchies.
Maybe it's just me, but I have no idea what you are asking for here.
You have to understand that the way you understand your application no one else does. That includes the underlying assumptions and "your" terminology. You have to be explicit when you ask these questions by providing detailed information and description for us to be able to answer your question.
We are not trying to be difficult, but just raising the bar in terms of the quality of questions, and answers where applicable. This is not a discussion forum but a Q&A site, where the question asked has to be clear and explicit and the answer provided should be concrete and accurate.
Anup