The Calvert Foundation's Community Investment Note lets users invest as little as $20 online in a host of social enterprises.

You can target the causes you care about most, choosing from health, microfinance, women investing in women, affordable housing, renewable energy or sustainable farming.

According to the foundation, investors can expect a 1% return over a year, 2% over five years, and 4% for a 15-year note.

Calvert doesn't invest in public companies, and investors will only fund enterprises that focus on creating social or environmental change.