Copied and mildly edited from my comment yesterday on the Joel On Software discussion board. The original poster, two years out of college, had asked whether to keep his college internships on his resume - and if so, how could he keep the resume down to one page?

Like any fairly ambitious person your age, you've got enough accomplishments, internships, gigs, volunteering, awards, etc. to fill at least two resume pages (reasonably typeset). That's great. So create that and keep it updated. That's your mega-resume. For each job, you have several bullet points listing all your tangible accomplishments and regular tasks you performed.

Then, for each individual job that you apply to, distill down a relevant one-page resume, with each item specifically selected for the job description and the research you've done on the organization. (You label your past gigs as "Selected Work Experience" so it's clear that this isn't all you've done. "Additional work experience and references available on request" is the last line.)

Once you're distilling a new resume for each job application, you clearly see that sometimes you should include internships, and sometimes another experience earns that space on the page. By the time you're 7-10 years out of college, you'll almost never find space for an internship on the one-pager.

If you're lacking space for a particular one-pager but want to convey your leadership skills, your experience in teaching could go in your "skills" section.

A few slightly off-topic tips:

1) Acquaintances and friends of friends are a better source than posted job ads. Talk to the most connected tech people you know, even if they're just acquaintances, and ask them to keep their ears open for opportunities for you. A personal introduction is a less brittle stepping stone than a resume.

2) Your mileage may vary, but the fact that I put "stand-up comedy" in my public speaking skills/experience line on my resume has piqued hirers' interest more than once. If you have a non-creepy hobby where you've accomplished a lot, think about putting it in the Skills section.