Imagine balancing college classes, internships, a part-time job and then signing up to work even more -- this time for free!  It's a new trend on college campuses. 

Co-eds are volunteering to shill for tech companies and they are getting references and experience that they can put on their resumes.

College sophomore Christi Williams passes out fliers and believes she's building her future in the fashion industry.   She's working as a student ambassador for the start-up fashion site, Stylitics.  And get this: she doesn't get a salary or college credit, but says she's getting something valuable.

"I'm learning a ton. And I'm definitely gaining a lot of leadership experience and I'm gaining lots of stuff to put on my resume," says Williams.

Experts say tech companies are flocking to college campuses, recruiting students to help them spread the word in exchange for gift cards, T-shirts and that all important resume building.

"Students have access to places that companies and marketing and marketers don't have access to. And so, for example, in a residence hall, students can promote things to one another in ways that companies could never do," says higher education consultant, Eric Stoller.

Companies ranging from Nascar to Microsoft are also in on the action.  The majority of students are not part of the company payroll, but they are getting something in return.

"We really focus on giving them a lot of perks, a lot of rich experience, strong networking," says Zach Davis, co-founder of Stylitics.

Student ambassadors do everything from handing out fliers to creating Facebook pages, producing YouTube videos, to hitting up the college paper.  Some companies are expanding to include high school students as well, something that does concern Stoller.

"I think that's pretty tricky. I think when you're dealing with minors I think that changes the landscape immensely. There's maturity issues involved. There's access, privacy," explains Stoller.

Another concern: ensuring enthusiastic ambassadors don't end up skirting college policies about marketing on campus.  Some schools have policies against distributing advertisements for a for-profit company.  And figuring  out the rules is often left up to the student ambassadors, who may be held liable if they violate them.

"The companies would say, well it's an unpaid ambassador program.  If the student gets in trouble, the onus is more on the student, which is unfortunate," says Stoller.

As for Williams, she says balancing school, work and an ambassadorship can be tough at times, but she believes it's well worth the effort.

"I'm growing a lot. I'm gaining a lot of leadership experience," she says.

These student ambassadorships aren't necessarily meant to replace traditional internships.  Many students take on both.

Williams believes her ambassadorship actually offers more national experience and networking opportunities than a local internship, and she hopes volunteering will lead to a paying job with the company in the future.