Very simple guide to using ufw to create firewall rules. `ufw allow ssh/tcp && ufw allow http/tcp && ufw allow https/tcp && ufw enable && ufw status` done. :-)
Handy article introducing chef and providing a few links. A little out of date now, but provides a useful intro.
Interesting article on how webpop built their infrastructure on Rackspace's cloud. Includes links to a few useful tools (chef, wormly, new relic, nagios, ganglia, and others).
Interesting article comparing Rackspace and AWS performance when applying high frequency trading strategies against 10 years of archive data. Rackspace io kicks ass, CPU slightly ahead.
CDN plugin for Magento that supports Rackspace and Amazon AWS CloudFront. Pushes images on demand, claims to be simple to integrate, and is free.
Useful article on how to deploy django apps on nginx. Handy.