Most company websites have a careers section where you can search and apply for jobs. Many professional and trade associations (such as American Society of Administrative Professionals or American Nurses Association) have related job listings. Be aware of potential job scams.
Search mainstream job search engines with keywords such as "work from home" or "work at home" or "remote" or "virtual".
USAJobs - What is a Remote Job?
AfterCollege
College Recruiter
CollegeGrad.com
CoolWorks - for seasonal or short-term employment
Lindsey Pollack: Multigenerational Work Expert
USAJOBS: Students & Recent Graduates
ZipRecruiter Recent College Graduate Jobs