To answer my own question somewhat, I found this post which listed these summer internships:
CERI Summer Research Fellowship 2022: announced March 2022 Effective Self-Help Internship 2022: announced February 2022
CHERI Summer Internship 2022: deadline March 2022 (not sure when announced)
ARC hiring round (includes intern opportunities): announced December 2021
PIBBS Summer Research Fellowship: announced December 2021
Redwood hiring round (includes intern opportunities): announced November 2021
SERI Summer Internship 2021: they seem to do rolling admissions which can start early
However, they appear to be quite US-centric.
To answer my own question somewhat, I found this post which listed these summer internships:
CERI Summer Research Fellowship 2022: announced March 2022 Effective Self-Help Internship 2022: announced February 2022
CHERI Summer Internship 2022: deadline March 2022 (not sure when announced)
ARC hiring round (includes intern opportunities): announced December 2021
PIBBS Summer Research Fellowship: announced December 2021
Redwood hiring round (includes intern opportunities): announced November 2021
SERI Summer Internship 2021: they seem to do rolling admissions which can start early
However, they appear to be quite US-centric.