Stars garnering dual nominations in the ensemble category include Chris Bridges, aka rapper Ludacris, and Terrence Howard for "Hustle & Flow" and "Crash."
In the film actress category Huffman will go up against Judi Dench, Charlize Theron, Reese Witherspoon and Ziyi Zhang. Her TV category, best actress in a comedy, includes Candice Bergen, Patricia Heaton, Megan Mullally and Mary-Louise Parker.
Ledger is up against Russell Crowe, Philip Seymour Hoffman, Joaquin Phoenix and David Strathairn in the best film actor category. Gyllenhaal faces Don Cheadle, George Clooney, Matt Dillon and Paul Giamatti for the supporting actor award.
The SAG awards were a good Oscar barometer last year, going four for four in the top acting categories, E! Online reported.
Shirley Temple Black will receive the union's lifetime achievement award during the Jan. 29 awards ceremony in Los Angeles.