All Industries

Indeed.com
Pulls job postings from multiple sites: company web pages, jobs.utah.gov, Craigs List, KSL, etc.
Glassdoor
An insider's look at jobs and companies. Interview questions and salaries are sometimes posted. You should first establish a free account (email rather than facebook seems to work better).
Looksharp
A resource to find internships and internship application resources. Used to be InternMatch.
LinkedIn Jobs
Allows you to harness the power of your network to uncover insights such as whom you know at a company, providing you an edge in your job search.
SimplyHired
Simply Hired is a vertical search engine company based in Silicon Valley, with the goal of building the largest online database of jobs on the planet. Their goal is to make finding your next job a simple yet effective, enjoyable journey.
The Muse
Great web site for all things job related.
Utah's Department of Workforce Services
Register to look for a job in Utah, schedule a workshop, get information on job fairs etc.
Utah 211
Find volunteer opportunities. Under 2) "Search click on service opportunity database." Search by types of volunteer position, zip code, etc. From the United Way.
Utah Nonprofits Association
Check out the job board and also look under the Membership Directory to get an idea of what is available.
Utah Hospitality Jobs
Jobs with hotels, resorts, and transportation companies in Utah.

Aviation

American Assoc. of Airport Executives
Good site for job-seeking aviation students.
ACI-NA
North American Airports internship page.
ACC - Airport Consultants Council
Nationwide internship opportunities.

International Internship Sites

Transitions Abroad
Good overview of interning abroad.
Going Global
Search, by country, for internships and jobs overseas.
Idealist
Jobs, volunteer opportunities and internships in the nonprofit sector.
Foundation for Sustainable Development
FSD achieves community-driven goals through asset-based development, international exchange and internships in Africa, Asia, and Latin America.
US State Department Student Programs
Student internships in an embassy overseas or in Washington, DC.
InternJobs.com
A global database of internships and entry-level positions for students, recent graduates, and career changers.
GoAbroad.com
Internship programs abroad.
Cis abroad
From site: "offers you the chance to work overseas for a month to a year. We customize each internship to your personal and professional goals: you can work in tropical rainforests, market products in fashion design, or guide tourists through museums."
isa
Internships and service learning. "Our team aims to help people like you find a different kind of experience abroad." Fee based.
Help International
Designed to empower people to fight global poverty through sustainable, life-changing development programs volunteer opportunities and internships.