The auction is being held on the Charity Folks Web site through April 12. More signed bones will be added for a two-week period as they are returned by celebs, the organization said.
Lauren Bacall, Doris Day, Paul Newman and Joanne Woodward, Donald Trump, Alec Baldwin, B.B. King, Tim McGraw, Morgan Freeman, Sarah Jessica Parker, Ryan Gosling and Betty White are also among the celebs who have signed bones.
Trump, host of NBC's "The Apprentice," autographed his bone in gold ink with the words, "You're Fired!"
White's bone has a hand-drawn photo of a dog with "Many thanks for helping" written in pink. The actress is a longtime animal-rights activist.
Last September, MARL auctioned 40 celebrity-signed bones, including those from Oprah Winfrey and Jake Gyllenhaal, at its second annual Fur Ball. The bones netted $40,000 for the construction of a new animal shelter, said board member Allison Nutt, chairman of the Fur Ball event committee.
Nutt said the online auction will give more people an opportunity to participate.
"We had people from all over the country call and want to know how to bid on the bones," she said.
MARL hopes to raise $50,000 from this year's auction, Nutt said.
Proceeds from the auction and this year's Fur Ball, to be held Aug. 16 in Jackson, will go to the new shelter's operating expenses.
MARL cares for 17,000 animals a year and services animals in a seven-county area in central Mississippi, said MARL Director Debra Boswell.
"We will be able to give more animals a chance to find a home," Boswell said.