new beginner to postgresql. Looking at it for a church

Hello:

I was wondering if anyone has setup a point-of-sale system with postgresql.
Also, I will have to create a database for a church that requires lots of
tables and subcategories. They have 4 different locations and wish to be
interconnected amongst each other, yet remain distinct and autonomous. They
have lots different categories (women's group, kid's group, seminars, etc.)
and funds within funds. Any suggestions/examples of how someone could go
about the data-modeling for this. Also, was thinking of using .php and ruby
to connect them via the net. I will also, require setting up a general
ledger and a full accounting system for them. Inventory for books, cds. I
am looking at multiple sources for them including MySQL, Microsoft.Net
(really, really don't want to go there) and any other suggestions
individuals may have.

Thanks and help is much appreciated.

Pamela