From Think Progress:
FINANCIAL SERVICES. The Small Business Administration will stop making loans, federal home loan guarantees will likely go on hold, and students applying for financial aid could also see delays and backlogs in applications.
ARMED FORCES. U.S. troops serving at home and abroad could stop receiving paychecks if the shutdown continues for an extended period and changes of station would also be delayed and facility and weapons maintenance would be suspended. Families back home would also be impacted.
HEALTH CARE. The National Institutes of Health will stop accepting new patients and delay or stop clinical trials. Medicare and the Veterans administration will continue paying out benefits, but new filers could face delays and doctors and hospitals may also have to wait for reimbursements.
PUBLIC SAFETY. The Environmental Protection Agency would stop reviewing environmental impact statements and food inspectors would stop conducting workplace inspections unless there is an imminent danger. The Bureau of Alcohol, Tobacco, and Firearms could stop processing applications for permits.
SECURITY AND TRAVEL. The Department of Homeland Security would suspend the E-Verify program, which helps businesses determine the eligibility of employees, creating hiring delays. The State Department will also likely halt new passport and visa applications.
PARKS AND RECREATION. The National Park Service sites and the Smithsonian Institution will be shutdown. During the 1990s, 368 sites closed down and approximately 7 million visitors denied entry.
DISASTER RELIEF. In preparation for a potential shutdown, the Utah National Guard is holding off on sending a team to help rebuild areas in Colorado devastated by massive floods last week. More National Guard engineers are desperately needed to repair major roads and bridges in Colorado. Roughly 240 Colorado National Guardsmen currently working on flood missions are also in danger of losing funding.