I recommend Conversion Rates Experts (http://www.conversion-rates-experts.com). Mainly, the CrazyEgg case study (http://www.conversion-rate-experts.com/crazy-egg-case-study/) -- love how they approach collecting qualitative data.

Also, the guys at Unbounce does a great job with landing pages A/B Testing (http://unbounce.com/blog/).

Patrick, a fellow HNer (http://news.ycombinator.com/user?id=patio11) writes a blog on marketing for software (http://www.kalzumeus.com/blog/) and other tips for developers.