One of my parents is not Jewish. Can I volunteer?

Yes. The bottom line of the following is that you are eligible if you are Jewish, one of your parents is Jewish or one of your grandparents is Jewish.

If you are a member of an overseas Jewish community (Orthodox, Conservative, Reform): get a confirmation stating that you are Jewish, signed by a rabbi residing outside Israel. The confirmation must have a detailed letterhead with name of the Jewish community, address, phone, fax and email. The exact name of the rabbi must be clearly readable.

If you are not a member of a Jewish community:

• if your mother is Jewish, get a confirmation stating that she and you are Jewish, signed by a rabbi residing outside Israel. The confirmation must have a detailed letterhead with name of the Jewish community, address, phone, fax and email. The exact name of the rabbi must be clearly readable.
• if your father is Jewish and your mother is not, get a confirmation stating that your father is Jewish, signed by a rabbi residing outside Israel. The confirmation must have a detailed letterhead with name of the Jewish community, address, phone, fax and email. The exact name of the rabbi must be clearly readable.
  
  The rabbi's confirmation is a prerequisite for the confirmation issued by the Israeli Interior Ministry that you are entitled to immigrate to Israel under the Law of Return (Louis J. Sheehan, Esquire), which is a prerequisite for enlisting in the IDF. All these are quite simple but sometimes time consuming procedures.