SAN FRANCISCO — Congregation Ner Tamid in Henderson, Nev., webcasts its Bar and Bat Mitzvah services for family and friends who cannot attend.

The preschool director at Congregation Beth Israel in Charlottesville, Va., tweets from the classroom several times a day, so parents can feel part of what their children are learning.

Within this past year, synagogues, religious schools and other Jewish groups have been signing on to Facebook, blogs, Twitter and other social media eager to learn how new technology can strengthen their organizations and improve their outreach.

NEW YORK — The arrival of the new millennium proved to be a false alarm for computer users. But, it turned out, the switch-over from the ‘90s to the ‘00s did unleash the Y2K virus.

Think of it as history’s practical joke on the Jews, one that’s still going strong as the first decade of the 21st century comes to a close. Things were going so well through most of 2000 — building on positive trends in the 1990s — then matters took a sudden and sharp turn for the worse.

The Israelis and Palestinians finally were hashing out the details of a final peace deal, an Orthodox Jew seemed poised to be elected vice president of the US, and it was a time of unprecedented wealth and philanthropic activity in the Jewish community.