+1 on the coursera classes, Mr. Mehrling is an amazing teacher and really knows the subject well.
I finished part 1 of his course and am close to finishing part 2.
That's great, it seems like a bunch of happy "accidents" happened in connection to your activities as a blogger.
Was it a technical blog? What pushed you to start a blog in the first place?
This probably says something bad about me but almost everything good I have came through an accident followed by seeing it through rather than planning or setting goals!
The blog was just my personal blog. Being a technical person it had a technical edge but wasn't focused on that. I started a blog of sorts in 1999 (something called an "e/n" site which were the rage at the time - the infamous "StileProject" site came out of this era and genre) simply to share stupid photos, jokes, insights, and interact with people I knew online. Then I blogged constantly from then until Twitter took off (which somehow killed my personal blogging entirely :-().
I think I should start personal blogging again though exactly because of the happy accidents. You just don't get them as much through Twitter or Facebook because the content there is so ephemeral and not likely to come up in a Google search in a few years.
You might want to look into topic modeling to extract the most meaningful topics (set of co-occuring words). It could greatly improve your results compared to the keyword approach. Interesting initiative, keep us posted !
"What people would be willing to use" seems like a more fertile approach. Open your eyes and spot repetitive, boring task that one has to deal with on a regular basis !
If you have users, everything else with follow.
Good luck !
