I have just finished uploading a couple of new docs to the Discoverer site on OTN (link to site). The first is the "Capacity Planning Sizing Calculator 10g (10.1.2.0.2)" (link to .XLS file on OTN). This calculator has been updated for Discoverer 10.1.2.48.18 (which is the Discoverer version in the latest Oracle Application Server 10g Release 2 (10.1.2.0.2)). You can use this to get CPU and memory sizing approximations for Solaris and Linux. The Linux calculator is the new addition as we found that the number requests for scalability numbers on Linux had steadily increased since we last did the paper for 10g (9.0.4).
The second doc is a presentation on Discoverer 10g (10.1.2) Best Practices (link to PDF on OTN - it is a 2.9MB PDF file) that Mike Donohue had done at the 2004 San Francisco Open World. Highly recommended.