Book: High Performance MySQL (2nd Edition)
http://www.highperfmysql.com/

MySQL Performance Tuning - Best Practices:
http://jpipes.com/presentations/perf_tuning_best_practices.pdf

MySQL Index Tuning and Coding Techniques for Optimal Performance:
http://jpipes.com/presentations/index_coding_optimization.pdf

Web Performance and Scalability with MySQL:
http://develooper.com/talks/

MySQL Server Variables
http://forge.mysql.com/wiki/ServerVariables

MySQL Server Variables - SQL layer or Storage Engine specific
http://www.mysqlperformanceblog.com/2006/06/08/mysql-server-variables-sql-layer-or-storage-engine-specific/

“Show profile” + “Information_schema.profiling”
http://blogs.mysql.com/peterg/2008/11/06/show-profile-information_schemaprofiling/

PeterZ presentations:
http://www.mysqlperformanceblog.com/mysql-performance-presentations/

Using MMM to ALTER huge tables
http://www.mysqlperformanceblog.com/2008/03/27/using-mmm-to-alter-huge-tables/

MySQL File System Fragmentation Benchmarks
http://www.mysqlperformanceblog.com/2008/03/21/mysql-file-system-fragmentation-benchmarks/
http://www.mysqlperformanceblog.com/2008/03/18/working-with-many-files-and-file-system-fragmentation/