Scott Robbin from Weightshift posted a spot-on article about how front-end developers can improve the performance of the websites they build. He has three basic concepts you should follow (fewer file requests, download files concurrently and keep cache as long as you can) and shows examples for each one. His write-up came out of his talk at WordCamp Chicago but the techniques apply to any CMS.
Though, the talk itself was WordPress-specific, the underlying concepts are applicable to any client site, whether it be coded in WordPress, Expression Engine, MovableType or none-of-the-above. At Weightshift, we have made performance tweaking a standard part of our development cycle on all projects. I