I have finished Hansen and Quinn’s Greek course and feel I am competent in Attic Grammar and syntax, but my vocabulary is extremely limited. Does anyone know where I can find a substantial vocabulary list online?
If there is a particular text you plan to tackle, you can always try the Perseus Vocabulary Tool which will give you a custom vocabulary list for one or more texts.
[They seem to be having some server problems, but a few refreshes usually does the trick.]
Rather than obtaining a vocabulary list, I recommend diving straight into whatever text you want to read, and just looking up vocabulary you don’t know. It’s more interesting that grueling vocabulary list memorization, you see it in context, and you learn the vocabulary you actually need. For me, that was/is the most effective way of inflating my Greek vocabulary.
There are worse places to start than the GCSE exam list of required words: http://www.aqa.org.uk/qual/pdf/AQA-3024-W-SP-06.PDF.