Improving Application Performance
The TechEd 2004 sessions are available. This session talks about performance and the Performance Modelling process. Mark Russinovich's session also looks interesting. There are also the 64-bit session and an AMD64 session - the performance figures for the AMD Opteron 1P vs Xeon 3.2GHZ 2P are impressive. Writing Faster Managed Code session covers a lot of the usual ground; however the final few slides have some interesting data on Longhorn performance expectations.
Update: Looks like you now need a username/password to access the TechEd 2004 sessions :(