In no particular order... we love them all!
Ahrefs is an excellent source of link data and is probably a very wise choice for any digital marketer looking for more than just that link data alone.
Majestic still remains one of the main sources of link data available and has been a tool we have used since the day they launched.
Sitebulb is a great little crawling tool, well created, very client focussed and the creators of the greatest release notes in SaaS
Little Warden helps you track changes on your client sites. Created by the family team that we used to work with at Kerboo.
Women in tech SEO is an amazing community created by Areej Abuali and do amazing work in supporting women and diversity in our industry.
A great newsletter from the ridiculously productive and amazing Aleyda, if you're in SEO its a must read each week to keep informed.
If you're a practicing SEO and don't have a copy of Screaming Frog somewhere on your machine, are you even an SEO?