The bad news first: ReGreek, which was a really useful online New Testament Greek resource, has gone the way of the dodo. I’m still not sure I totally understand all the intricacies of what happened, but it sounds not dissimilar to the legal flap between Warner Bros. and Fox over Watchmen — basically, permission had been given to use something (in this case, a version of the UBS critical text) by somebody who did not have the right to give permission. That may be a crude and inaccurate representation; see here and here for more information. Alas. This means I’ll actually have to look things up and analyze forms when I read the New Testament now… sigh.
On the other hand, another really fantastic, if old-school, resource which just came to my attention is the Google Books online verson of E. A. Sophocles’ Glossary of Later and Byzantine Greek from 1860. I discovered this while doing my own translation of the long prayer of consecration in the Divine Liturgy of St. Basil (which will be its own post here shortly). I have to take a diagnostic Greek test this fall, so I’m taking the opportunity to work through various texts, looking up even the words I think I know just to familiarize myself better with various nuances, principal parts of verbs, etc. Anyway, I came across the word σαρκωθείς, and while its meaning was obvious both from context as well as knowing what σαρκ- means and also being able to clue into the fact that there was a theta at the end of an aorist stem (that means it’s formed off the sixth principal part of the verb, that is, the aorist passive), but I nonetheless wanted to find it in a dictionary. Well, Messrs. Liddell, Scott, Bauer, Danker, Arndt, and Gingrich were collectively no help, so I started searching for the word online. This search led me to the Sophocles, which, as expected, gave me the dictionary form σαρκόω, meaning “enflesh”. It otherwise seems like an excellent resource, and I will be adding a link to it under the Greek Resources tab. (Although, when I post on the prayer of consecration, I’ll have to talk about the two words which weren’t in BDAG or Sophocles but were found nevertheless in Liddell & Scott.)
Finally, the Dynamic Horologion and Psalter just rocks. Period. The service texts generated appear to assume that a priest is not present, and not quite all the service text variables are worked in yet (stichera at “O Lord I have cried” during Vespers, for example), but it nonetheless seems incredibly useful.
Leitourgeia kai Qurbana: Contra den Zeitgeist 
While perhaps not as convenient as Regreek for NT Greek, I have found both http://unbound.biola.edu/, and http://biblos.com/ to be helpful.
Interesting. Both of those sites use the UBS text in one capacity or another. I wonder if they are ultimately going to run into some of the same problems.
There is also the Church of Greece Bible website:
http://www.myriobiblos.gr/bible/default.asp
And then this site for Greek liturgical texts:
http://analogion.net/glt/
I’ll add these to the Greek resources page as well.
E.A. Sophocles online. Καλα!