She said the show of support demonstrates to military families that "America has your back."
The first lady and the vice president's wife, Jill Biden, launched Joining Forces in April to try to motivate citizens, businesses, non-profits and community groups to do more to support military families. Since then it has resulted in the hiring of 16,000 veterans and spouses, and pledges to hire another 25,000.
Thursday's announcement of 100,000 additional job commitments for military families includes plans to hire at least 5,000 wounded veterans. At the same time, the first lady announced an online Veterans Job Bank tool to help veterans and spouses search for jobs with military-friendly employers. The tool already has identified 550,000 job postings.
Mrs. Obama, in prepared remarks, said the new efforts are "part of a wave of support forming that stretches across this country."
"There are millions of Americans all across this country who are working hard every day to find new ways to honor military families' service," Mrs. Obama said.
She was to announce the commitments in a speech at the U.S. Chamber of Commerce, which has at times had a prickly relationship with the Obama White House, differing over policies on job creation, taxes and regulation.
Chamber President Thomas Donahue said the partnership between the business group and Joining Forces was working to "create an environment in which thousands of military veterans and military spouses can find meaningful employment in their local communities."
Brad Cooper, executive director of Joining Forces, said the effort to encourage hiring of veterans and spouses has exceeded expectations as companies adjust their goals upward after meeting initial hiring targets and finding that military families provide skilled and loyal workers. Some of the jobs for veterans represent net job growth, while others are a result of turnover, he said.
Unemployment is particularly high among veterans of the wars in Iraq and Afghanistan. The Labor Department estimates that 12.1 percent of veterans who served in the military since the 9/11 attacks in 2001 were unemployed in October, higher than the national rate of 9 percent. Among veterans under the age of 24, the rate was closer to 22 percent.
Thursday's hiring commitments include plans by the International Franchise Association, which represents 1,100 franchises, to hire 80,000 veterans and spouses by 2014. That number includes 5,000 so-called wounded warriors.
Steve Caldeira, president of the franchise association, said the structured nature of franchises and their need for employees committed to "operational excellence" make them a good fit for those trained in the military. Examples of franchises that have made hiring pledges include the UPS Store, Arby's, TSS Photography, FASTSIGNS, Mr. Rooter, TeamLogic and Valpak.
Mrs. Obama also announced that the Military Spouse Employment Partnership, launched last summer and made up of nearly 100 companies and organizations, had committed to hire 20,000 military spouses. The organization includes companies such as Microsoft Corp. and Home Depot, and franchises such as Data Doctors and Guidant Financial.