I just attended CapitalCamp in DC, and one of the sessions was High Performance Drupal: Step by Step.
The slides from the session are available on the page referenced above. The presenter, Fabian Franz from Trellon, made one point early on:
"If you build the house on one pillar, it'll not hold long ..."
Then went on to say the four pillars of high performance for Drupal sites are:
- Pressflow / Drupal 7
- APC
- MemCache
-
Varnish and Boost
It may not possible to use Pressflow (with an installation profile). In that case he suggested to use the other three.
The slides have a little more detail though the presentation included much more, and he showed how quickly all four could be added using command line His style is a somewhat unusual (you'll see if you check out the pdf), and the information seemed good. See what you think.