Buy vs. build
Baseline has a good, common-sense article on buy vs. build decisions. Nothing ground breaking here, but the method presented should suit most straightforward analyses. The spreadsheet that they have developed is intended for use with a function point based analysis, but could be adapted to other measures of software size.
p.s. Overall, I'm impressed with Baseline, especially for a free rag. The analysis is usually good and the articles are, for the most part, relevant and useful if you are in a corporate IT or development environment. You do have to sign up to see most of the articles.