Warren Trenchard's book is a fantastic resource for building vocabulary as well as for reference and review. This revised edition contains many updates that make it even more 'user-friendly' and comes with a hardcover binding that will make it hold up to the repeated use it will get.
The first section of the book lists words by their cognate group and is obviously the section to use in order to rapidly build a working vocabulary. Trenchard also lists the frequency of occurence of each word in this section, so students can decide which words are most important to memorize at first (however, with the cognate approach, it's easier to memorize many words that occur infrequently as well). Following this section is another section that lists words only by their frequency, from most frequent to least frequent.
The third major section provides the principal parts of all the verbs in the GNT. It is best used for review or for reference on those occasions when your mind just goes blank. If you are not careful, however, you will come to rely on this section as a crutch and will likely never memorize the principal parts of all verbs. Again, when used as intended, this section is valuable, but if you let it become a crutch, then it will actually become an impediment to learning Greek verbs.
Trenchard also provides a list of all proper nouns, which (for reasons I've never yet been able to figure out) tend to be omitted from a great many lexicons. He also has a catch-all section of 'Other Lists' that provides number words, Aramaic words, Hebrew words, and a slew of other useful items.
This is the definitive book for students who are building their NT Greek vocabulary. If you find this volume to be a valuable tool, then check out Trenchard's "A Concise Dictionary of New Testament Greek" as well (see my review of that book for more information).