Some study aids which I recently came across

Sing and Learn New Testament Greek (CD)

Mainly this CD puts noun endings and verb endings etc. into familiar tunes. Frequently the lyrics are not make up of words, but of endings. Well this kind of songs is not to my taste. It sounds so meaningless and awkward. I don't think I can memorize the endings like that. I prefer the endings to be rehearsed together with real words in memorable and meaningful (and fun) contexts.

Song School Greek, by Michelle Hahne

(Children's book with CD which has songs)
This is pretty cool.

Label your stuff with NT Greek

Here are ten Koine Greek words for objects in your house or apartment, such as "pen" and "key." All are from the New Testament. Do you remember where do these items appear?
I've just written labels of these things and stuck them on the objects in my room. I think it is a fun way to familiarize oneself with NT Greek words.

e.g.

1	lightning (electricity)	ἀστραπη	f
2	towel	λεντιον	n