I did not see the site of Laura Gibbs for Croy's "A Primer of Biblical Greek" mentioned...the course was given in 2005, but designed for students to take online. Quizzes and some extra credit material no longer available, but lots of drilling practice, guidance through Croy's book, and audio are still ready and waiting for anyone that wants it. Looks ideal for self-study.
More to the point, it goes through Croy's book in 15 weeks, and looks to provide as thorough introduction as any. A good summer project:
Online Koine Course using Croy: http://www.mythfolklore.net/bibgreek/
I recently exchanged an email with the professor regarding this course--and where to continue once I've finished. She has recommended the Athenaze text, which I plan on combining with one of the more intensive textbooks (I've chosen Mastronarde over Hansen&Quinn). She recommended going through a Homeric Greek textbook shortly after the classical Greek textbooks, to help solidify what has come before as well as open up this branch of literature. Seems like sound advice!