http://www.day32.com/MySQL/

This script takes information from "SHOW STATUS LIKE..." and "SHOW VARIABLES LIKE..."
to produce sane recomendations for tuning server variables.
It is compatable with all versions of MySQL 3.23 and higher (including 5.1).

Currently it handles recomendations for the following:
# Slow Query Log
# Max Connections
# Worker Threads
# Key Buffer
# Query Cache
# Sort Buffer
# Joins
# Temp Tables
# Table (Open & Definition) Cache
# Table Locking
# Table Scans (read_buffer)
# Innodb Status

Recent Changes
# Correct awk display error which formats integers > 4294967296 in scientific notation.
- Was manfest in MEMORY USAGE section where total system RAM > 4GB.
# Fixed rounding error where mysql will lose 4K from the join_buffer_size value.
- Other values may have the same issue but are not yet reported
# Added support for FreeBSD and MacOS (thanks Sam and Geert)
# Added support for Solaris
# Changed how system memory is derived on Linux.
- Use /proc/meminfo vs free -b and avoid inclusion of swap space.
# Include note warning of instability when key_buffer_size > 4GB in versions 5.0.51 and lower