I hear it more than anything else lately.

 

List Scalability is there anything on it?  Yes, there are a few solid resources that I recommend...

 

 

Case Study by MCS and Knowledge Lake on Extreme Scalability - June 2008 - customer requirements (10.5 million content items stored in the database, 54,000 new content items per day, and 400 concurrent users) while consuming less than 50 percent of the overall system resources. Thanks Paul Learning. (He's the one that shared his results with me... early)

 

How to Plan Server farms for Scalability - whitepaper - Feb 2008

 

Capacity Planning for SharePoint - whitepaper - This is about right sizing your farm from Memory to Disk to CPU.  There is some about capacity boundaries and perf counters to watch.

 

Plan for Capacity Boundaries - (Technet article) This is where all the numbers, charts and all the good, easy to read stuff is.  You won't find much prescriptive guidance though.

 

If this list isn't enough for you... I compiled a Mega List of Key SharePoint Capacity Planning Articles, Tools, Testing, etc... from blog posts to whitepapers to articles.

 

If you haven't visited these three sections on TechNet since Feb 2008, you should.  They've been reorganized and are much easier to walk through. 

 

The New Microsoft IT SharePoint Performance Optimization Paper has some great references on best practices.