Whether visiting Israel as a volunteer or tourist, it is worthwhile your time to get to know some of the ins and outs of the Hebrew language. If you really get into learning, you can consider Ulpan (Hebrew language school). But just to get you started, here are some websites and applications that you might find helpful.
Google
Websites:
http://www.milingua.com/ (Free for beginner levels)
http://www.morfix.co.il/ (Free Hebrew English dictionary – but you have to know the Hebrew alphabet)
https://translate.google.com.br/
Free Apps:
Morfix (Free Hebrew English dictionary – but you have to know the Hebrew alphabet)
Quizlet (Design your own flashcards)
Google Translate
Paid Apps:
HebrewVerbs (Conjugation tables for Hebrew verbs)
Flashcards Deluxe (Avanced flashcard system that allows you to make use of Hebrew Siri)
Hebrew Pretati (Hebrew phrase book)