The German Bible Society has a really nice website where you can access their critical editions. See here: BHS, LXX, NA27, UBS4, Vulgate and more
One cool way to use the site is to link to specific passages in blog posts or tweets. For instance, here, you can check out the story where Paul preaches so long that a guy falls out of a window and dies.
Navigation within the Bibles is very easy, they use unicode fonts, and according to the website, these are the "official internet editions." :-) How can you go wrong?