Happy New Year!
I just heard about OpenEngagement: a Plone bundle designed for the accounting industry. OpenEngagement provides document and web content management services and has a portal to be used to share documents with clients. OpenEngagement's revenue model is based on support contracts and a hosted option.
The initiative appears to be backed by CaseWare, a provider of specialized assurance and reporting software to support the delivery of accounting services. There is an integration with CaseWare's flagship product (WorkingPapers) that allows you to browse the document repository from within WorkingPapers.
This seems like a good use of a community based content management project like Plone. For minimal cost, CaseWare is able to provide their customers (and prospects) with decent content management functionality. The small to medium accounting firms, which make up a large portion of the accounting industry, are traditionally under served in this area. The support option is probably very desirable because many of these companies have minimal in house I.T. resources.