I had the same feeling with my previous job. I wasn't doing any good for society. Starting out happy, after five years, I was just too tired of all the shit and eventually resigned. It actually got to the point where I resigned before I had gotten a new job.
My takeaway is this: If you feel bad about your current job and its contribution to society, start applying for other jobs. Just find something that looks better. Do it now. There are both jobs and businesses out there that aren't all bad. Once I quit I felt a huge relief, and after starting my new job, I've never come close to being as tired of work as I once was. (I'm working for the government now with no particular individuals earning too much off of me.)
Another option is of course to start your own company, if you feel you're up to the task. I kind of have a dream of starting my own company, not take out all the profit for myself, but as profits grows, hire people and giving them good conditions whatever job they're doing. Spread out the wealth and set an example for others. But I'm not there, and I probably never will be.
Someone mentioned education earlier. I think education is one of the areas I think humanity can benefit greatly from computers and software. The Khan Academy mathematics web training is a great example. There is no good reason why textbooks, instructional videos and interactive exercises shouldn't be free these days, and there are probably ways to get governmental financial support for this in Denmark. All the mathematics, physics, chemistry, geography, language and social sciences we currently need to learn the first 8 years of schooling isn't really evolving that rapidly either, so good learning software would probably just need minor updates now and then.
After education, environmental issues are probably next in my book. But I feel they're connected in may ways. Education for everyone is crucial to understanding the importance of our current environmental issues around the world. It's also a fact that rise of education leads to fewer kids in a population, reducing the overpopulation of the earth.
Then you have distribution of wealth, which was you first point. In our part of the world we actually have the position to speak up against inequality, and we should use it. In other parts of the world, you can be too poor to have the means or energy to stick it to the man, because everything is about survival for the next couple of weeks. The western, developed world exploit the third world systematically to get cheap goods. We consume way more than our fair share of the planet's resources. But the ways our goods are produced aren't transparent, which is why we agree to keep up with it. We don't see all the child labor and the slaves who work 70 hours a week for almost no pay.
In short, the world is rotten and unfair, and my only advice is in my first paragraph. Don't let the world bring you down, but don't accept the current state either. Be happy but rebellious and do not accept unfairness.