I will give it a go....
and of course have to put in the usual recommendation about the Sage Handbook of Qualitative Research :$ even if you aren't doing qualitative work, it still is an excellent source for this kind of stuff...
Paradigm--the big "box", framework, platform, world view ( pick whatever works for you) from which you are doing your work.
Ontology, epistimology and methodology are like the three legs of a stool that make up your paradigm. All three combine to make up your research paradigm.
Methodology is just the "tools" by which you do your research ( ie interviews and how you examine the data, or whatever)
Epistimology--what is knowledge--what is the view on where knowledge comes from, how it is formed ( ie for constructivists, knowledge is formed or constructed through social interactions..) ( or in a positivist framework, knowledge is that which is deduced and proved through appropriately reliable and valid tests)
Ontology--what is truth or what is reality--how do you discern what is "true" within your research? Constructivism might say that reality is socially constructed, positivism asserts that there is a verifiable and universal "truth" to find, etc...
The Sage Handbook has a handy chart that makes all of this very simple and understandable.