501 Japanese Verbs by Roland A. Lange
This book comes from the makers of the highly popular 201/501 verbs series. As the name implies it provides full conjugations of 501 important Japanese verbs. And when I say full, I mean full. This book has verb forms I've never seen anywhere else. The book is completely in Japanese-style romaji (zi for ji, hu for fu, etc.). I don't see this book being incredibly useful since Japanese has far fewer irregular verbs than most languages, but it's good as a quick reference and to make sure you've conjugated a verb correctly. One good point is that it provides honorific and humble forms of verbs, which you can't find just anywhere.
Japanese Verbs at a Glance by Naoko Chino
This is a great book for Japanese learners from beginner level to intermediate. It covers all of the verb conjugations and details polite forms, requests, and all other important verb uses. It also goes into important word patterns such as wa iu made mo naku ("it goes without saying that...") and many others. The book has at least one example (usually two) for every item presented, and each example is presented in Japanese characters, romaji and English. If you're stumbling across word patterns that you don't understand, it's very likely that this book explains them. I highly recommend this book for any beginning or intermediate Japanese learner.
At the end of the book is an appendix that gives conjugations of about 150 important verbs in the 11 main verb forms.