We can talk as much about the principles of Open Source and Free Software, the philosophy, why freedom matters, etc. This is important, but these are not the answers that most of the students are looking for.
Most of us eventually want to land a lucrative or satiating job as a software developer. Having a knack for problem solving and a passion to achieve it using programming is prerequisite to fulfill this desire. There are people who care less for a job but have a zeal for problem solving using programming. Open source is good for all types of folks.
‘Kay, I love programming, but how does Open Source help?
We do a lot of projects as part of the curriculum. On finishing, all that remains of the project is a plain description in the resume. Instead of this, you can open source your project and host it on a service like github/sourceforge.net. This way, you are opening your horizon to the whole World Wide Web, rather than confining you ideas to a few fellow students.
The Working Environment. The best thing I like about open source projects is the style of working in general. You learn how “actually” a software is built. Typically, every software company trains it’s employees how to work in such a collaborative environment. Trust me, employers want you to be productive as soon as possible, and your exposure to collaborative environment gives them the confidence to recruit you.
Responsibility. You hold the responsibility of making something which will be used by hundreds and thousands of people. Get involved in HFOSS.
Experience. In many situations, you are bound to work on technologies you have never played around with. Open Source projects give you the experience in such technologies.
Money. Participate in Google Summer of Code :P
Fun. Yes, you read it right. Ask anyone who is involved, it gets better and better as you keep contributing.
On an ending note
A college student just like us once thought of developing an operating system kernel as part of his hobby. He released it as open source so that more people could use his code, analyse it and give feedback.
In a span of few years, major corporations like IBM started using that code and eventually recruited developers to extend it.
Today, all the big names like IBM, Intel, etc have developers under their rolls working on the same piece of code.
By the way, its Linux ;-)