Cross processing is developing film in the "wrong" chemistry, for example shooting slide (E6) film and processing it in the chemicals meant for colour negative (C-41) film. This is normally what’s meant when people say cross processing, but it can go in almost any direction. You can also do C-41 film in E6 chemistry, or any film in B&W chemistry. The only thing you can’t do is B&W film in colour chemistry, because the bleach leaves you with a blank roll.
Apparently "film acceleration" is a bit more complicated, and sounds a lot like something called the "Henry Beck process" that the owner of my local lab told me about (and I can find absolutely no information on anywhere). Instead of a simple chem switch, this is: underexpose slide film, pre-soak, soup in B&W developer, wash, fix, wash, bleach, C-41. Yeow! But the results do look unique.
Read the how-to, with sample images, at JPG Magazine.
Flickr member pochedunfou also has a large set of accelerated photos, which serves as an excellent reference of the effect across a number of different emulsions of varying age.
Update: pochedunfou pointed me to the Be Great: Accelerate group for the technique on Flickr. Cool!
acceleration, alt process, alternative process, cross processing, film, xproRelated posts
New Kodak Ektar 100 film replaces 100UC
Kodak to discontinue 400UC film by year's end
Free film offer from Fujifilm UK (London only)
Hope for Polaroid 20x24 & 8x10 film?
Holy shit: "Filminator" DIY film coating machine
Wow. Thanks for the cool link! Looks like a fun thing to try out…