Stanford CS Theory
Computers, Computer Science, Theoretical, Research Groups - Stanford CS Theory. Research includes sequential and parallel algorithms, computational problems in databases, computational geometry, design and analysis of programs and programming languages, and combinatorial, logical, and algebraic mathematics.
http://theory.stanford.edu/
ACM SIGACT
Computers, Computer Science, Theoretical, Research Groups - ACM SIGACT. Association for Computing Machinery Special Interest Group on Algorithms and Computation Theory.
https://sigact.acm.org/