Some of the biggest names in computing will visit Purdue while you are here. Some of the visitors are big-names-to-be. When they visit, you want to attend these talks. Some will be boring, some will be incomprehensible, but they will give you a view of computing and current research that you probably can't get any other way. You might even get an idea for a research topic from the talk.
The current faculty sometimes give talks, including CS590 and CS690 seminars. Again, this is a good way to get exposure to some interesting research and faculty here at Purdue. Although you may wonder about it sometimes, the CS faculty here at Purdue is one of the best in the country. Take advantage of your time here to hear what they think is interesting.
If you are planning on getting a Ph.D. here, you probably also want to attend Ph.D. prelim and defense talks by other students. This is the best way to find out what is expected for a Ph.D. degree, and to see what kinds of topics are of current interest. It is also a good way to get some insight into potential advisors.
If a faculty search is on for the year, there will be lots of faculty candidate talks in the spring semester. Attendance at these talks is beneficial both to you and the department. The department takes into consideration feedback from students when making a hiring decision, so please attend these talks and give your feedback to a GSB representative after candidate-student meetings which will be announced at least a week in advance.
In approximate order of appearance, the big departmental social functions are:
Starting with the 2006-2007 school year, the department funded a weekly social hour. Each week a new host, either a an organization, research lab, or CS administrative office, bought food and beverage for everybody to enjoy while they mingled. These occur on Friday at 3 PM.
The GSB hosts numerous events for graduate students each year. These include pizza socials, bowling, BBQs, and Q&As with faculty (over topics like getting an academic job, whats going on in the department, etc.).
link to gsb events page