What Don points out is true - a lot of variables can go into stiching a photo together. Photoshop's own Photomerge and other stand alone programs can do a lot, but there are times when you've got something beyond what these programs can handle effectively.
Do you want to go with a medium format setup, or 35MM? Horseman makes panoramic cameras, and I think that Fuji has or had one as well. There's also a small company ( English, I think ) called Horsley that makes them as well. All kinds of options exist here, including going up to a 4x5, and cropping the image panoramically ( I know, some might call that cheating, but what the hell.... ).
As for a scanner, I believe that Epson has one in the Expression line that can scan up to 4x5 size negs or transparancies - so an Xpan neg would work fine on that.