Fedified.com is a list of Twitter-verified accounts that have moved to Mastodon. This is a hand-curated list, so it's updated a few times a day. https://fedified.com/
Fedified — Notable Twitter accounts on the Fediverse

Protecting public figures, journalists, creators, companies, and brands on the fediverse by verifying common ownership of Twitter Verified and Mastodon accounts

Mastodon 🤝 Twitter Verified ➡️ Fedified
@taylorlorenz when I try to click through from the mastodon handles to follow the people it doesn’t work and prompts me to migrate my account (?!) but if I just go back to the main Mastodon instance and search the names I can easily follow them. One solution: make this an exportable CSV file that I could then import and follow many of them with a couple of clicks. Any more detailed guidance as to how to use this list efficiently without having to click many times for each name?
@HelloAndrew @taylorlorenz if these are all account you already follow on twitter, you can try a tool called debirdify: https://pruvisto.org/debirdify/ which allows you to automatically find available mastodon equivalents of accounts you follow on twitter and export them as a CSV. I hope this is helpful!
Debirdify

This is a web app that helps you find out which of the people you follow on Twitter are on Mastodon/in the Fediverse already and follow all of them easily.

@HelloAndrew @taylorlorenz It requires you to authorize it to access you twitter account, so be mindful of the possible security risks. Here’s a toot by the creator of debirdify, Manuel Eberl, introducing the tool: https://graz.social/@pruvisto/109257404426481007
Manuel Eberl (@[email protected])

Okay, I hacked something together that tries to figure out if the people you (or somebody else) follows on Twitter have Mastodon account. Here it is: https://pruvisto.org/debirdify/ Very experimental. Not sure if I will keep it online forever. I'll put it on Github as well some time soon I think.

graz.social