Source: http://grok-code.com/58/the-power-of-a-programming-portfolio/
Portfolios have been used for years by architects, artists, and designers, but why not for computer programmers? A programming portfolio is a great way to showcase your best work, and highlight your involvement in challenging projects. It provides a great talking point during an interview, and gives more insight into your work than a resume alone could. A programming portfolio can help you stand out from a sea of other candidates.
- Stand out from the crowd.
Very few programmers have portfolios. Judging by the candidates I have interviewed, I would guess less than 5% take the time to put together a portfolio of their work. So just having a portfolio in the first place can put you ahead of a large number of potential candidates when looking for a job.