Edit 2023-02-05: @ElenLeFoll has done a great video on using Debirdify. https://www.youtube.com/watch?v=PMzB2h2noEA
Edit: Twitter has blocked Movetodon. Try one of the other services below.
Given that twitter is going to start charging for api usage next week, but has neglected to give anyone any info about rates, I recommend running https://www.movetodon.org/ one last time while you still can.
None of the migration tools will work after the 8th (give or take some timezones).
Here’s a list of similar services operating as of 2023-02-04
Debirdify https://debirdify.pruvisto.org
Fedifinder https://fedifinder.glitch.me
Twitodon https://twitodon.com
Mastodon Flock https://mastodon-flock.vercel.app
Flock is the easiest to use, despite the hilarious Windows 95 UI. It actually adds the follows to Mastodon, the others export a CSV file which you can import in the import/export section of your Mastodon preferences.
Twitodon found far fewer acounts when I used it (20 vs. 112). I don't recommend it.
Fedifinder scans lists as well. It also will recommend a Mastodon host to use based on where your friends are. (You can use it before you have a Mastodon account.)
Debirdify will search people who follow you as well. And also tells you which services it thinks you should use. Can also read lists, and gives a very long summary. But I get very confused as to what I'm exporting if I also do lists. Basically, if you want to import lists, do them first, they include everyone you follow. Also, don't freak if it just sits there for a while doing nothing--it will refresh the screen eventually (with great charts). But do double check and make sure there isn't an error in there about rate limits--it's hard to spot.
Not working:
Movetodon https://www.movetodon.org/