I recently put together an email for some colleagues with a few links to various resources that were related to some questions about scalability vs. performance that I received. These links are good resources for any developer or systems administrator interested in scalability. I thought this might also be useful to others facing growing web applications.

Distributed Caching with Memcached - This is a good foundation article on the use and implementation of memcached.
http://www.linuxjournal.com/article/7451

Good memcached FAQ - Very nice FAQ for memcached. Touches on some items that are a little harder to find elsewhere.
http://www.socialtext.net/memcached/index.cgi?faq

memcached at Facebook - A little article about how memached is used at Facebook. A little dated but useful.
http://lists.danga.com/pipermail/memcached/2007-May/004098.html

LiveJournal Architecture Links - Studying LiveJournal's architecture is worth your time. They made memcached.
http://danga.com/words/2005_oscon/oscon-2005.pdf

http://www.slideshare.net/vishnu/livejournals-backend-a-history-of-scaling

A broader view on Scalability with some good information
http://www.slideshare.net/techdude/scalable-web-architectures-common-patterns-and-approaches/

Quite Good overall PHP-centric performance article in the context of Javascript.
http://www.thinkvitamin.com/features/webapps/serving-javascript-fast

XDebug and KCache Grind - Learn to profile your applications. Profile often and early to avoid problems later.
http://xdebug.org/

http://kcachegrind.sourceforge.net/cgi-bin/show.cgi

APC Opcode Cache - No well dressed PHP application should be without a good opcode cache save resources.
http://pecl.php.net/package/APC