Thanks to UTAGS President Nick Karrick for the reminder on these.
Check the
ESRI Careers website and pay particular attention to the Student and Grads section. There are opportunities in everything from software design to GIS to marketing and accounting.
For those eligible, you should be applying for the
ESRI UC Summer Assistantship. It appears that to be eligible you need to be a student when you apply. Deadline is early April and in the past it has required a reference letter so don't wait until the last minute. I had this opportunity as an undergraduate
student many years ago and loved it.
Maxar (formerly Digital Globe, a remote sensing and analytics company) is also
looking for interns. Use the check boxes to narrow your search criteria and be sure to check the length of time that a position has been posted.