I found this today: http://www.networkedcorpus.com for visualizing the results of MALLET topic models, by reference to exemplary passages. Its creators explicitly contrast this with index building by hand… more about all that later; here’s how to get it working for you.
See the documentation at https://github.com/jeffbinder/networkedcorpus
Install python 2.7, numpy, and scipy. Download the installers, and follow the instructions.
Then download the networked corpus zip file, and unzip it somewhere on your machine.
In the networked-corpus folder, there is a subfolder called ‘res’ and a script called gen-networked-corpus.py. Move these two items to your Mallet folder.
Generate a topic model as you would normally do, from the command line.
Then, type at the command prompt:
gen-networked-corpus.py --input-dir <the folder with your original texts in it> --output-dir <the name of a folder you'd like all the output to be in>
Navigate to that folder in your browser, open the index.html and voila.