This list might be with a look of you want to keep an eye on the various tools. Source: almost 3 years ago

How Search Works - how Google crawls the web and indexes the content. This video by Paul Haahr - a Google engineer is awesome to get a good understanding of how it all works. Also, this video by Martin Splitt is great to get an understanding of how JS sites work in search. You might also find some of the stuff in this list of beginners section useful. ( PS: That is a list I maintain ). Source: about 3 years ago

Apollo.io seems popular for cold email. Source: 7 months ago

FAAANGM + ATlassian/Uber and similar product based companies 85 lacs - 1.1 cr Startups like coinbase / apollo.io / rippling 80+. Source: 9 months ago

Their data seems pretty good and their features are awesome, but they had a couple of glitches this week that are annoying me. I know they seem to be the best, but has anyone bested them yet? Curious if there's anything out there that's better than Apollo.io. Source: 11 months ago

Tons of options: apollo.io is popular and affordable. If you're looking for recently funded company contact info, saasydb.com is good. Source: 12 months ago

I agree with most people here in that its invaluable. Especially when paired with some other tools like apollo.io and autobound.ai. Source: 12 months ago