This is how Zhubert describes the resource:
Complete GNT online - source text is from jtauber, based on Nestle Aland 26This site is well worth a visit and already does a lot of interesting things. Because the CMS is set up blog-style, you can also subscribe to its feed, and I've added it to my blogroll. I'll be keeping an eye on the promised developments.
Parsing - available for every word, just hover over the word with your mouse
Word Detail Page - click on a word while reading and see detailed information about that word
Word Study - from the detail page, you can conduct a study on every use of the form or the root
Graphical Occurrence - from the word detail page, shows occurrences of both root and form by book
Basic Root Definitions - simple lexicon entries, right now very woeful, from Perseus...soon you will be able to correct these!
Grammar Reminder - a simple reminder as to the most basic grammar via your sidebar
And more to come...suggestions welcome! zhubert at zhubert dot com
I have added a link to my Greek New Testament Texts page and with the promised additions, I can see this one moving up the page as time goes on.
Update (20:03): enthusiastic endorsements from James Tauber and Rubén Gómez.
Update (22:31): Tim Bulkeley also enthuses.