Supermarkets in the USA ca. 2001 allocate shelf space according to complex and varied deals with manufacturers and distributors, to the point that exact amounts of space (x inches) are specified in contracts at the main office. These allocations are constantly changing as new products come along, old ones fall out of favor, media hype helps or hurts, deep discounts are offered, and so on. A result of this is that some hard-to-define or multi-category items get put into entirely different areas from time to time.

An example might be those plastic 'roasting bags' where one places meat and spices in a sealed bag in the oven. Do those go with the spices? the gravy mixes? the butcher counter?

These categorization problems are invariably solved differently by different companies, and are the source of most of the confusion.

Some stores print maps, but those are usually only the big picture and details like the example above are lost.
Perhaps someday there will be kiosks with simple search terminals, like at some bookstores (i.e. Borders Books) where customers can type in queries. This would be a great additional revenue stream for the supermarket owners, as they could sell screen space for image ads, offers from competing brands, etc., much the way the "instant coupons" that are printed at the checkstand work.

Another potential solution would be to have wireless transmitters in the stores that would beam maps and complete indexes (plus the aforementioned ads and offers) to customers' PDAs. Perhaps one could enter a shopping list and have the PDA beep as one wanders the aisles to alert that an item on the list is nearby.