Here are some links to interesting things involving programming languages and their implementations.
ACM SIGAda,
SIGAPL
ACM Transactions on Programming Languages and Systems
Bill Kinnersly's Programming Language List
C++ Course
Complete Formal Semantics of Real-world Programming Languages
Functional Programming Archive
Gamelan's Java Repository
Logic Programming
Object-Oriented Programming
Parallel Programming Reading List
PCCTS (yacc-like system)
Research Language Overviews
Researchers in Programming Languages and Compilers
Scheme Repository
Vienna Development Method (it was used to define PL/I)
Visual Programming
Z Notation for Specification