Here you’ll find links to various MySQL tuning guides.
If you have the money, you may wish to buy various books on the subject. But if you can’t buy the book, or in a hurry, then this post is for you.

If you know any other article which is not here yet, please feel free to let me know.
Thanks.

1. How to monitor MySQL Performance : Indeed, how can you optimize when you don’t know that something needs to be optimized.
2. My previous post on the subject
3. From ProfitPapers.com – when you need MySQL to perform under much bigger load.
4. MySQL Performance Blog : as the name says, read it from beginning to the end to gain huge insight on the topic.
5. Top Performance Tips : 1. Index. 2. Don’t index everything. 3. etc. Good stuff.
6. MySQL @ BSD tuning guide (thanks dikshie)
7. “Change threading, from NPTL to Linux Threads; by specifying LD_ASSUME_KERNEL=2.4.0” (thanks Priyadi)