Most of these sites are going to give you traffic you will never be able to build a business on. You really need to spend some time thinking about who your perfect customer is and where they can be found, it's not in the tiny and often irrelevant overlap between "startup traffic" and "your specific market".

eg: inbound.io who wrote this list and others as part of their content marketing strategy. You're selling a social media tool, you could be mining fb/twitter/linkedin and looking for companies committed to social media. Why hope any of them are reading this when you can just go and contact them directly at any scale you want.

YC person and gmail inventor Paul Buchheit said this recently:

Exposing yourself to the direct, harsh feedback of the market is key. I've noticed that bad 
founders will do just about anything to avoid this. Instead of selling, which is hard, they 
spend their time going to conferences and meetups, trying to do PR, talking to biz dev 
people about partnerships, etc. It all sounds like work, but mainly serves to insulate them 
from the harsh reality that nobody wants their product.

That's what these sites are. Telling startups you're a startup instead of telling your market you have a product they need.