The following are major web sites that focus on jobs in GIS and related fileds:

• GISjobs.com
  
• GIS Jobs Clearinghouse
  
• EcoJobs (Environmental Careers Organization)
  
• URISA (Urban and Regional Information Systems Association - GIS is part of their broader agenda)
  
• ESRI (publishers of ArcGIS products, often have jobs available in software and services)
  

You can also check with your local university or college - many such institutions have GIS centers or at least programs (such as Geography or Planning) that have GIS courses and/or majors.  Students looking for part-time work and graduates may be available to help you.  LEARN MORE about staffing your GIS program...