Thanks to Andy Rowell for passing this one on. The German Bible Society has made available free online versions of its texts, including the NA27, the Septuagint and the Biblia Hebraica Stuttgartensia. It is a very attractive user interface, with nice unicode fonts, browsable and searchable.
There is no critical apparatus available (yet) but this is a very welcome development. I have added it to the Greek New Testament Texts page.