Ancestry.com has special testing for that as well as 23andme.com.
,Are you Jewish?
Do you have Jewish roots? Are you an Ashkenazi? Are you a Levi or a Cohen?
A DNA test by iGENEA provides you with clear evidence of whether you have Jewish roots. Based on your specific genetic characteristics, we can identify whether you are of Jewish descent, which line the Jewish descent is from (paternal, maternal or both lines) and even to what percentage you are Jewish. In addition, your profile is compared with more than 700,000 people in our database. If we find a genetic match, i.e., people with whom you correspond genetically, you may contact these people and intensify your family research."