What is it?

I've not used but I guess is a list of email adresses
to spam and be spammed from. Some people told is good
to get referrals.

That's pretty much true in my experience. I think the best way to use a safelist is to pay for a pro membership in a very large safelist.

Yes a safelist is a list of e-mails that you can send to automatically through the website.

Make sure it's a paid safelist. If it's a free safelist, most of the members will probably use a junk mailbox (which they will never even open) so your ad might never be seen.

Try:

GoldenWealth Safelist
The Wealth Connection
ZenOfSafelist Safelist
PaidBanners Safelist
Cash4USafelist

And that's about all I can think of that actually gives response...

By the way, if you see anyone advertising one of those junk mailboxes, spam them to death.

Interesting advice there.

Wait a minute...if they are using junk mailboxes, how are we going to spam them?

Oh yeah! Spam them until they go over the limit!

i think large safelists have little advantage.... i advise to register for a small safelist something with no more than 500 members. (like my safelist check my signature )
the best feedback i had using a safelist was from a safelist that was in the begining of it's existenz and had only about 100 members. and the feedback was great. i can tell you that because that time was the only advertising method i was using. The amount of messages was'nt excessive and when i was checking my mail i would at least read the topics.