I like to teach using the teacher's manual for Claro que si! An Integrated Skills Approach, by Lucia Caycedo, Debbie Rusch and Marcela Dominguez. This is a difficult text for students but the workbook for Claro que si! (Student Activities Manual Workbook, by Lucia Caycedo, Debbie Rusch and Marcela Dominguez) is a better choice for students to have. These books include Spanish and South American variations of the language.
Other good books are: Practice Makes Perfect: Spanish Verb Tenses by Dorothy Richmond, Practice Makes Perfect: Spanish Pronouns and Prepositions by Dorothy Richmond and Spanish, the Easy Way by Ruth J. Silverstein, Allen, Ph. D Pomerantz, and Wald, Ph. D Heywood. This book is oriented toward the Mexican variation of the language.
Spanish - English Visual Dictionary by DK Publishing presents mostly Spanish and English nouns using photographs of the objects.
There is a pocket translator by Franklin, the Franklin Spanish/English Dictionary, featuring downloadable content capability. This is an amazing translator with conjugation and tenses.
Finally my husband Don likes to play with the program Easy Translator 4. Like any computer program it's ability to do correct translations is limited but you do get to do interactive practice and that is attractive to some people.