My biggest involvement during grad school was with SOCHI, our student organization for HCI. I served as an officer for three semesters, and during that time we became the most active student SIGCHI chapter in the country. Here are some of the things I've done for SOCHI:

During my time as a SOCHI officer, I've helped organize a total of 7 'design jams', which are events where we work with a company to solve one of their design problems. During these three hour events, students work in groups to brainstorm, ideate on whiteboards, and sketch solutions.
Our design jam "clients" have included four partnerships with Mozilla ("design the browser of the future", "improve tabs", "design for a windowless browser", "redesign browser history"), as well as Zattoo, TechSmith, and a designing for disabilities session.
We've been featured many times on the Mozilla Labs blog.

My submission with Chris Hanrath on "Search in a windowless browser" was one of the finalists in Mozilla's Spring 2009 Design Challenge.
My submission to the Mozilla Design challenge on "designing the browser of the future" was voted second place by SI students. I created a lightweight mockup and screencast to describe my idea, "Browser Spaces".
In October 2009, I organized SOCHI:Ignite, an event where HCI students talked for 5 minutes about topics of interest, in the style of the O'Reilly Ignite events.
My talk was about my experiences with self-initiated projects during grad school, called "Choose your own adventure: how to extend your learning outside the classroom".

In October 2008, I gave a Tech Talk to fellow students on how to use Axure prototyping software.
Later that year, I secured $3,120 in corporate sponsorship from Axure to help our 5 Michigan CHI Student Design competition teams attend the CHI conference.
→Axure blog post: "Axure Supports HCI Students to Compete at CHI"

In October 2009, I organized a "sketchnotes" activity for those attending our department's symposium lecture by danah boyd. I organized the 8 submissions into an online sketchbook, and publicized the collection. You can see the collection here.

We also hold numerous career-related events, such as peer reviews of portfolios and resumes, and peer advising sessions on how to get internships and jobs.
In a separate role from August 2008-April 2009, I served as the HCI Peer Advisor, holding office hours to answer student questions and serving as a liasion between students and the HCI faculty.

Finally, I wrote content for our SOCHI website and posted event updates and links on our SOCHI Twitter account.
You can check out the SOCHI website to see some of my blog posts and more details about our past events.