you don't have to be a student or pay the university to use the library.
(You can also work at Harvard and get a library card as a perk. I often contemplate this fact.)
The good news is that MIT has a much more awesome library and you can, in fact, turn up in person at MIT as a civilian and read copies of Nature. Of course, you have to make the time to do that. The parking is tricky, so you'd best ride the train.
Even in the Boston area I have yet to find a neighborhood library with a Nature subscription.
If, in fact, you know where I can legally get access to, say, the Nature and Science journals without either paying hundreds of dollars a year or physically traveling to the local college library please, please paste the instructions here.
Sorry. :(