Generated clusters... now what?

[Mark]

I am playing around with clustering and I just generated my clusters 
using KMeans. I'm able to view my clusters using clusterdump and they 
appear to be pretty good. My question is now what can I do with this 
data other than just inspect it using clusterdump?

For example how can I ask:
    "What cluster does document #1 belong to?"
    "What are all the documents belonging to cluster X?"
Thanks