Mary Johnston Letellier
Bel Canto: A Theoretical and Practical Vocal Method
I cannot speak highly enough about the book, Bel Canto: A Theoretical and Practical Vocal Method.
It has such a wonderful variety of exercises, working on such technical challenges as mesa di voce, portmanteaus, shakes, trills, scales, patterns, and breath support. If you are a teacher running out of ideas for vocal warm ups or a student wanting to vary your warm up routine, this book is a must.
I highly recommend picking up a copy of this wonderful resource; you can find it here new for around $15 or used for around $5. Enjoy working your way through the book!