UPDATE: if anybody using Aperture 3 happens to read this, I've made the cross processing preset available for download here: http://pixpeep.com/misc/cross_process.zip --- I wrote an article that documents my attempt at cross-processing in Aperture - which I did by trying to match the look of a photo cross-processed in Photoshop. I got pretty close to what you can do in Photoshop, and give the exact steps (so you can create your own preset to do the same thing). However, it's not perfect... I do notice a little bit of harshness in the dark red areas, due to my adjustment of the black point in the red channel. Using curves in Photoshop seems to give greater control over the contrast in those areas. I'd be interested in seeing if anybody can improve on it. I think it works pretty well, although I can understand now why some have complained about the lack of curves in Aperture.