A very simple search engine dedicated to the plumbing trade. The idea is that hard-to-find spare parts will be easily found when the plumbing supplys shops signup and upload their stock.
Only stock that is on the shelves will be loaded - no prices, just quantity. Let just my stock do the searching for you, rather then phoning around or loosing a sales lead.
The data is uploaded as a CSV file and is then broken down into manufacturers making it very fast to search. No RDBMS - just good old Perl scripts!