One of the best things you can do for this purpose, while getting a modest ROI on a passive investment, is invest in a company that profitably does whatever you want to see more of.
For example, you could invest in a for-profit company that sells needed goods to low-income people at lower prices. Something like Wal-Mart, which is one of the most effective anti-poverty engines in the US. You might also say the same of something like Aldi (owner of Aldi stores and Trader Joe's), which is a discount store chain. This is true even though a company like Wal-Mart is seeking to make money first. Its customer base tends to skew heavily towards low-income consumers, and historically to rural and elderly consumers. When Wal-Mart is able to provide food, clothing, appliances and the like to poor people at a lower cost, it is making it marginally less painful to have a low income.
Peter Suderman can explain why Wal-Mart is a humanitarian enterprise:
Walmart’s customer base is heavily concentrated in the bottom income quintile, which spends heavily on food.
The bottom income quintile spends about 25 percent of income on food compared to just 3.5 percent for the top quintile.
So the benefits of Walmart’s substantially lower prices to the lowest earning cohort are huge, especially on food.
As Suderman points out, this view of Wal-Mart dramatically lowering prices that low-income people pay for food was corroborated by an Obama adviser.
That's just one company. You can pick the industry and company that best suits your personal preferences.
Alternatively, you could invest in something like Whole Foods, a company with multiple missions to improve the planet and the community, in addition to the more typical mission of being a prosperous retail chain.
Of course, as a general proposition, a less than entirely altruistic, charity-inclined investment doesn't need to be targeted at those with low incomes or at saving the planet. You could invest in almost anything you think is good (yachts, yo-yos, violins, energy production, industrial inputs, music performances) and the company will take care of making more of that good thing. You didn't say whether your goal was to help the poor, the planet, arts, sciences, knowledge, community, or whatever.
What I understand you to be saying is you are willing to accept a lower ROI in exchange for some warm-fuzzies from your investment. That seems perfectly valid and reasonable to me, but it makes it much more subjective and particular to your tastes. So you'll need to pick something that's meaningful to you. If you're going to trade ROI for positive feelings, then you should pick whatever gives you your optimal blend of emotions and returns.
Alternatively, you could invest in something stable and predictable to beat inflation (some sort of index or fund) and then annually use some portion of those profits to simply give to the charity of your choice. Your investment and your charity do not necessarily need to be the same vehicle.
