Roman Abramovich - Yes, Jewish:
"Of Jewish background, Abramovich is a firm supporter of Jewish causes in Russia and Israeli causes, and has funded several projects in the Abramovich neighbourhood in Jerusalem, and in Tel Aviv. In addition, he is the richest Jewish person in Great Britain."
See also: http://www.somethingjewish.co.uk/articles/1857_richest_jews_in_brit.htm
Ben Stiller - Yes, Jewish:
"Christmas has always been a confusing time for movie star Ben Stiller, because his parents insisted on following both Catholic and Jewish traditions. Stiller's mum Anne Meara is an Irish Catholic, while his father, funnyman Jerry Stiller, is Jewish."
Orlando Bloom - No, Buddhist, apparently:
However, he used to think he was Jewish...:
"loom had thought that his father was South African-born Jewish lawyer Harry Saul Bloom, but during his younger years and after Harry's death, Bloom's mother revealed to him that his biological father was actually Colin Stone, a family friend."
Nigella Lawson - Yes:
"She traced her mother's side of the family, the Salmon, (originally Solomon) family, owners of J. Lyons and Co.) to Ashkenazi Jewish ancestors in the Netherlands and the Rhineland of Germany."
Scarlett Johansson - Yes:
"Her mother, Melanie Sloan, comes from a Bronx-bred Jewish American family,"
"Her parentage is – mum’s side, Jewish family from outta the Bronx."
Adam Sandler - Yes:
"Adam Richard Sandler (born 9 September 1966) is an American-Jewish actor, comedian, producer, and musician (he sings and plays the guitar)."
David Beckham - 'Sort Of' (Probably not practising, and getting into Scientology a bit with Tom Cruise.):
"His maternal grandfather is Jewish, and he has spoken of the influence the religion has had on him but is not known to practice Judaism or any other faith, though he "has been seen [wearing] red Kabbalah bracelets"."
As an aside, it is important to note that there is a difference between being of the Jewish race (having Jewish heritage) and and being a practising Jew. People from either of these groups may be referred to as Jewish, but some people of jewish ancestry who do not practise the religion may not identify themselves as Jewish. It is often difficult to work out which of these categories (if any) a person will belong to.