CSS-Tricks has a useful snippet showing how to make exceptions to .htaccess password protection based on the requested URL.
TJ Stein gave a really good presentation at WordCamp Chicago 2011 about scaling and performance issues with WordPress installations. He focuses a lot on using ngnix instead of Apache, but also covers PHP object caching, Varnish, CDNs, benchmarking, etc. It’s a good overview of current practices, but there’s also a lot of specific tips throughout.
Mark Maunder benchmarked several performance tuning measures with a WordPress installation on a VPS server to show which are most effective. The biggest improvements were from installing PHP-APC, setting up Nginx to proxy concurrent connections for Apache, and using MySQL’s query cache.
Jason Diehl describes the right way to setup directory permissions on a Linux box running Plesk so that WordPress can automatically create the directories it uses to store uploads. Basically, you need to make sure that PHP’s safe mode is turned off and that wp-content is owned by apache, in the apache group, and chmod’d to 777.