For me it's still residential real estate. We own 6 homes, 5 of which are rented out. A property manager manages 4 of them and my parents live in the 5th at reduced rate (very responsible, no issues).

I rarely hear from the property manager, he just runs large expenses by me, tells me when tenants are leaving and always has another lined up, recommends when we should replace carpet/appliances/paint, etc. My largest time commitment is during tax time since I still do our taxes.

For more detail see my post on 2014's passive income: https://news.ycombinator.com/item?id=8118022 The only significant change is that our property in San Diego has appreciated significantly over the last few years. When I wrote the comment above I hadn't looked at the current appreciation, but I was way off. One of our properties has approximately double in value from what we paid for it and the other two have increased by at least 60%. Rents haven't increased near as much, but we've added around $50/yr to the rent. The vacancy rate in San Diego is ultra low, so the market supports it.

Note: Some people say property managers aren't worth it, but the good ones are. We've had to fire a couple, but the one we have in San Diego now is stellar. We've never had a property vacant for more than a week or so. If I'm busy, it may take me a month to find a replacement tenant. That month of lost rental income more than cover property management fees, not to mention the headaches it saves me.