If you google for free ad posting sites or free classified websites you will get thousands of sites. There are lots of free sites where you can post you ads, below are some websites where you can put almost any type of ads.
I believe classified sites are still best for promotion. Although we have social media sites people go for classified sites too. Classified sites are best to promote any single product or service. Classified websites are not to post affiliate links still you will see some and ads which is not ordered properly. So, most of the time ads do not get visitors but most popular websites can help in this because they manage posts regularly and the ad post expires to get fresh ads listed on main page and under category.
There are lots of classified websites
Where many sites are closed, we have still websites which is running and people are satisfied with their service. Free classified websites would be best choice if you can not afford for advertisements but paid classified websites is best to get attenuation in first visit to the website.
Free classified website
Many sites have closed there service, I listed some of checked and active classified websites below.
OboAds free classified website stay for 90 days and feature ad starts from $2.50
Indian classified websites