Passover is a Jewish holiday. It begins on the 15th day of Nisan (on the Hebrew calendar), which falls between nightfall April 2nd and nightfall April 10th. Passover commemorates the exodus and freedom of the Israelites from ancient Egypt. In Israel, Passover is a 7-day holiday, with the first and last days celebrated as a full festival (involving abstention from work, special prayer services and holiday meals). In the Jewish diaspora outside Israel, the holiday is traditionally celebrated for 8 days (although Reform Jews celebrate for 7 days), with the first two days and last two days celebrated as full festivals.
Good Friday is the Friday before Easter or Pascha. It commemorates the crucifixion of Jesus at Calvary. This year, it is on April 6, 2007.
Good Friday is a holy day observed by some Christians. Special prayer services are often held on this day with readings from the Gospel giving accounts of the events leading up to the crucifixion. Mainstream Christian churches view Christ's crucifixion as a voluntary and vicarious act, and one by which, along with resurrection on the third day, death itself was conquered.
Easter celebrates the death and resurrection of Jesus as the basis for the salvation of mankind. Easter this year will be April 8th. It falls on the first Sunday after the first full moon of spring.
Jews celebrate the Passover (commemorating their freedom from slavery to the ancient Egyptians).
Good Friday falls on the Passover weekend, and that is the day that Jesus died on the cross.
Easter is the day that Jesus rose from the dead (on that Sunday).
So Christians celebrate Good Friday and Easter.
But, because Jews don't believe Jesus to be the Saviour, they don't celebrate the latter two holidays.
Hope that helped you out.