I built a little hobby poetry editor on Heroku in my spare time and I was really concerned that, although I have no ads or anything, the poems were hard to focus on with everything going on around them. So, I made a little button called "Reading Mode" that hides every element on the page except the poem text and a button to return to full mode.

I think it definitely improves things--at least for the types of people who actually read poetry. Would love to see this approach on a lot more sites. I'm sure there are great examples out there.

Here's the URL: http://poetry.heroku.com

EDIT: Heroku currently has a DB issue, which they're working on. Link still down, but hopefully up soon.