Never mind all the snow and ice outside, summer internship season is already under way. This is the time of year when college students clean up their resumes, research companies, and speak with employers all over the country. These opportunities often pay well and allow students to build up their work experience and network before graduation. Naturally, getting an internship with the right company is important.

So which companies have the best programs? The Glassdoor fourth annual intern survey shows that tech companies are, by far, the most popular with students. About half of the twenty-five companies listed are in the tech sector. Facebook sits at the top of the list once again, while Google was pushed to No. 3 this year to make room for Chevron. Other tech companies on the list include eBay, Yahoo, Apple, Microsoft, and Intel.

The other half of the list covers a wide variety of industries from manufacturing and consumer goods to entertainment and energy. Energy companies Schlumberger and ExxonMobil also made the list. NBCUniversal and The Walt Disney Company represent the entertainment industry, and insurance companies State Farm and Liberty Mutual make an appearance as well.

What makes a winner: impact, career development, and perks
Part of the appeal of tech companies is that intern projects often yield immediate and important results. "Millions of users used my project," said a Google software engineering intern in New York City, "so even as an intern, I really felt as if I was making an impact." A Facebook intern, also based in New York, liked the chance to work on "interesting problems, which actually affect more than a billion people."

Many of these companies offer special events for interns. An eBay public relations intern in San Jose mentioned "mini-summits with [CEO] John Donahoe and other executives," while an NBCUniversal intern in New York liked the professional development sessions.

A software engineer intern at National Instruments in Austin described a program that included "training, intermediate evaluation, and feedback sessions with a supervisor and an exit interview." A video for the top company, Facebook, describes the internship experience as a hands-on job tryout.

Beyond professional development, the top companies offer some awesome perks -- they are courting college students, after all. These range from small delights like "bagel Wednesdays" at eBay and social outings at Epic Systems Corporation all the way up to free housing like that provided by Qualcomm in San Diego -- two bedroom apartments with paid housecleaning service and utilities. In fact, free or heavily subsidized housing has become a fairly common perk among tech companies, something students should consider as they weigh their internship options.

Internship opportunities by city
As part of the survey, Glassdoor has also compiled a comparison of internship opportunities in major U.S. cities using recent listings on the site. Perhaps unsurprisingly, New York and San Francisco led the pack in terms of internship openings. Chicago, Atlanta, and the Dallas-Fort Worth Metroplex offered lots of options as well, while Tampa and St. Louis were more limited.

Career information tailored to college students
Glassdoor has also debuted a new resource for students, focused on internships, entry-level jobs, compensation, and job search advice. Because the Glassdoor database and employee reviews cover everything from entry-level to executive positions, the sheer amount of information can be overwhelming to novice job hunters.

Glassdoor for Students gives them the most relevant information, including jobs that are popular with recent graduates and companies that are currently hiring. Reviewers can also tell others about their interview experiences to better prepare users for the application process.

Companies to watch
The Glassdoor survey and city data can also be useful to investors and trend-watchers. The companies that are most in demand for internships are the ones that have the pick of current college talent -- talent they can bring back full-time after graduation if they choose to make an offer. Competing firms with weaker internship programs are at a recruiting disadvantage, especially as the economy continues to grow.