I know A and I will do cross processing (http://www.aandi.com), but I haven’t ever used them for it, and they aren’t exactly cheap. If you’re trying to get black and white transparencies, you might also want to take a look at DR5 (http://dr5.com/main.html) – they have a process that makes positives from several kinds of standard black and white film. Again, though, I haven’t used them.
i haven’t tried it with b/w, but i don’t know that you’re going to see much of an effect. most cross processing goes E6 film in C41 chemistry…i think doing it the other way just gives you desaturated colors etc. YMMV, though, i’ve never done it C41 film->E6 chemistry.
Fantastic effects can be produced with black-and-white photography. It is important that photographers keep the special needs of monochrome photography in mind when they are shooting pictures. Black-and-white photography is all about contrast, so look for ways to bring that out. Lighting across the shot reveals texture and depth. Low light conditions often reveal subtleties not seen in color pictures. Also look for patterns, shapes and irregularities in the frame. These are what stand out in a black-and-white photo.