NEW YORK - Heath Ledger's death has spiked sales and interest in the late actor's films. As often happens after the death of a famous actor or musician, many have sought to revisit or simply discover his work. Three of Ledger's movies charted among the 25 best-selling DVDs on Amazon.com as of Friday afternoon. Most have been purchasing copies of Ledger's 1999 comedy "10 Things I Hate About You" and his 2001 period action flick "A Knight's Tale." After those films, Ledger pursued more dramatic, challenging roles, with 2005's "Brokeback Mountain" — the third most popular of his DVDs on Amazon — being roundly considered his finest achievement. The 28-year-old Australia native died Tuesday in a Manhattan apartment. Toxicology tests to determine the cause of death will not be completed for at least a week. Ledger's latest film to be released, the multi-persona Bob Dylan film "I'm Not There," has mostly completed its theatrical run. It played in only 61 theaters last weekend. The lone theater it remains playing at in New York is the Film Forum, an art house and repertory theater that has been screening "I'm Not There" since it was released in November. "The film is doing very well and as long as it does well, we'll play it," said Film Forum first-run programmer Karen Cooper. "I don't imagine that it's going to do better because of his loss. I think it's doing as well as it is because it's a very strong and interesting and unusual film." The impact of Ledger's death on his last completed project, "The Dark Knight," remains to be seen. The latest installment in the "Batman" series, Ledger plays the Joker, and his dark, twisted take on the villain had been a focal point in the film's advance promotion. Since Ledger's death, over seven million have flocked to YouTube to watch trailers of "The Dark Knight." Over one million have watched a clip of an interview where Ledger discusses the Joker role. Warner Bros., the studio distributing "The Dark Knight," has not yet announced any change in schedule for the film, which is planned for a blockbuster summer release on July 18. "Certainly `The Dark Knight' is one of the most anticipated films of the year," said Paul Dergarabedian, president of box office tracker Media By Numbers. "I think Warners is just going to stay the course and keep marketing the film." As for its box office performance, Dergarabedian suspects the film is so big that it "kind of transcends almost anything like this that might happen." He adds that the film's release will to a certain degree honor Ledger, whose performance was already expected to impress moviegoers. At the time of his death, Ledger was in the midst of shooting "The Imaginarium of Dr. Parnassus," a $30 million film directed by Terry Gilliam. The movie recently completed shooting scenes in London and was soon to resume production in Vancouver, British Columbia. Producers have not said whether the film will continue or not. In the film, Ledger was to co-star with Christopher Plummer, Lily Cole and Tom Waits. Options open to producers — depending upon how many scenes Ledger had left to shoot — include recasting (and thus reshooting) his part, finishing it with the help of a body double (as was done after Brandon Lee died while making 1994's "The Crow") or simply canning production. Ledger had also been preparing to make his feature directing debut by adapting Walter Tevis' novel "The Queen's Gambit." In an interview last month with Variety, Gilliam told the trade paper: "Heath is extraordinary. He's just so good, and he's going to be a film director. He's watching everything, and he's going to be a much better director than I will ever be."