Companies spend a lot of effort doing all sorts of "brand building". Usually this involves advertising and showing your customers how you're the best. The effectiveness of this is debatable: how many people actually listen to broadcast advertising and just how often do they remember the message? My favorite example is a video advertisement I saw many years ago. It was a beautiful Rube Goldberg machine made from auto parts. After seeing the ad, I remembered that the ad was entertaining, but I didn't remember the auto company whose ad it was. What a waste! They were trying to build a brand-name, and that was the one thing I didn't remember: the brand name. Even in the job market companies often proclaim how their workplaces are better, how the company is like a family. Again, the impact of this advertising is debatable.
Google seems to be perfect at brand building, at least in the job market. Google's Summer of Code is a perfect example. They provide money for students across the world to write Open Source software. Google doesn't dictate what projects students work on, and they are happy if the software is not of immediate interest to Google. They want to make Computer Science students work on programming. Some of these will continue programming and will want to work for Google when they graduate. They've built a brand very early. Students remember that they were paid handsomely for their skills back when they were poor. Further, these students are the perfect audience: they are smart, dedicated, and self-motivated. When these students seek employment, they look towards Google as an example of a company they'd like to work for. This is a relatively small amount of money for Google, and the goodwill among students and open source projects is immense. I'm really surprised that other companies don't do this.
(Disclosure: I work for Google, and I participated in the first Google Summer of Code when I was a student.)