If you want to create something you have to create something. From all your ideas you have to pick one and build something. Build it as fast as you can, let people know about it, see if they find it useful, listen to their feedback, and remember everything they find wrong.
Then decide - push this through to the next stage, or scrap it and start again. I would say you should go 80/20 - 80% push/change/adapt/enhance, and 20% scrap and start again, using what you've learned.
Toss a coin - two heads in a row you scrap it and start over. That's close enough.
If you sit and try to find the best idea, or if you take someone else's idea and try to build it, you won't learn anywhere near as fast. You need to think of something that you would use, and build it. Give yourself three days to build, one day to deploy, one day to advertise, and two days to gather some reaction.
> ... visualization for website visitors ... nodes are different pages, edges are the links between pages ...
Can you do better than this:
http://www.solipsys.co.uk/new/SiteMapExpt.html?HN
Or this:
http://www.solipsys.co.uk/new/PaulGrahamEssays.html?HN
Can you do that for any site?