not much help for you, but we are developing own modules - but its realy specialized for our company and our system we use
i changed the templates to hide the price for not logged in users, wrote a complete new price function, a new module to register to the shop (well they no longer register to magento itself, data goes into own table, is imported to our main system and then back importet to the magento store) and we have a new module to show orders, cause we have to list orders which are made via telephone aswell…
each distributor gets on member account which stores all the orders and each membere of this company buying stuff from us gets an own account which is connected to the company account.
the problem is, that all that modules are made to fit our company and system, which will not work for other companies…
if you guys need some more info bout the concept behind our connection between our main database and the magento store - gimme shout