I recently took several course at Hebrew College in Boston. These are the recommended Hebrew dictionaries:
Professor’s First Choice:
Multi Dictionary-Bilingual Learners Dictionary, by Edna Lauder & Liora Weinbach ($36).
A smaller dictionary with 82,000 entries:
The up-to-date English-Hebrew Hebrew-English Dictionary, by Shimon Zilberman ($12.75)
Both are available at the http://www.israelbookshop.com/Israel Book Shop, (800) 323-7723, and possibly through other online booksellers. I do not sell these on my site.