501 French Verbs by Christopher and Theodore Kendris is an excellent supplementary text, particularly for beginner French learners.
Ideally, this book will be used to help familiarize oneself with some of the common and important verbs while learning and recognizing the appropriate conjugation rules. By the intermediate French learning stage the learner might find this book a little too bulky to be used as a quick reference and find it contains a number of repetitive and extraneous pieces of information (eg. conjugation of regular verbs is the same, so why include a full page for each one?).
There are multiple versions of this book so be sure you are buying the latest (or the earlier version if you intend to). I would recommend the latest version as it includes additional language reference material and a CD with various exercises. Price ranges for the various versions of this book vary considerably.
I have seen new copies on sale for anything from about $12 to $23, so search diligently for the best deals.
•Pros: -Ideal for beginners (ie. written in English)
-Over 500 common French verbs fully conjugated
-Introduction to French tenses with English examples
•Cons: -Less durable (ie. paperback)
-Limited utility for advanced French learners
I recommend this resource for the beginner to intermediate levels. For a more advanced resource look at Bescherelle.