There are none that have a high degree of accuracy.  The so called free ones are seldom worth the cost.

I found truepeoplesearch.com the best free provider of contact info. 

The addresses are in the tax records. Make your initial contacts by mail.

For free I've found fastpeoplesearch.com useful...

I do not have any recommendations for cost effective options.  The best option is to go out and meet lots of people.  And we still do mask and all.  People are hungry for contact with another human.  A

Sorry A I've never made a practice of cold calling people.  Be aware of the do not call list before you start any calling program.  CYA

I do not.  Why would you need cell phone numbers and emails for property owners? 

I used to use one that was good & went out of biz. Then I went to another on a monthly basis which was ok ($8.99?) but I can't remember their name either.

I have no idea. Just be careful that those you phone are not on the DNC list. It will cost you more than you'll make off of the list!

Generally, I search whitepages.com too.

Tax rolls is your best bet....That info has to be foolproof or you get a tax lien

I don't know of a service to lookup cell phones

Hard to get cell phone numbers and even emails these days.

Supervisor of Elections.  In Florida, you can request the voter file for the county.  They will send you an enormous csv file.  It's free.  From there you can search by name, address, or anything else.

Not everyone puts their phone number and email on the voter registration, but many people do.  Also, sometimes people are registered to vote at a house they do not own.  So you need to use this in combination with the tax records.  Look in the tax records and you see that John Jones owns the home.  Then look up in the voter file to get his phone number and email.

This works in Florida.  Other states have different public record laws then we do, so I don't know if it works everywhere.

I use to use haines, but seems like mailing post cards was just as effective. I think Haines costs twice as much as Cole. https://www.haines.com/real-estate-lead-generation/

Intellius was good, but I think their prices have increased. https://www.intelius.com/

I think Pipl also raised their prices to be out of reach and not make sense for most agents. https://pipl.com/

In Canada, this goes against the privacy act. 

Caller Smart works to some extent.