Where do private owners advertise units for rent?

[Jerry N.]

It has been a while since we have actively advertised apartments for rent and are surprised to see sites that now charge for advertising, when so many used to be free.  We tried Domu once, maybe three years ago, to see if it yielded anything different.  Domu was very new then and advertised all over the el.  There was nothing memorable about it except it was the first time we had paid for advertising. Craigslist and Zillow both charge now, not much but when you are used to free advertising...
Wondering if this is a recent change/trend and what I'm going to find looking at other sites we've used in the past. 

Where are you advertising these days?