Is there a way for finding out if the Pokémon Go servers are accessible?
While I don't believe there is an official server status page yet, MMO Server Status now have a Pokemon GO status page:
There is another site now that is also tracking the server status:
This site crowd sources the server status by clicking one of the UP, UNSTABLE, or DOWN buttons.
Although this question is already a few days old, I want to add my status page. Other than the site from cmmcd, the status is checked every 60 seconds through the Pokémon GO API. Hope you like it too. Have fun playing! :)
Might as well add one more... =P
Pokevision (and I) use http://ispokemongodownornot.com/.