I found, one nice article on OTN, for Invoice processing within SOA environment .
Moreover, SOA (Service-Oriented Architecture) is still a hottest topic since past couple of years. SOA is still have confusing term because it describe two different things. The first two word(Service-Oriented) describe a software Development Methodology, where as word architecture , simply represent a pictorial drawing of all the pieces that used put together in formation of Business process. What you say..
Expert's simply redefined SOA , as strategy that proclaims the intention to build all the software assets in the company using SOA methodology.
The 'Services' referred to in SOA are software Chunks or components , constructed so that they can easily linked with other software components. At the core of servicss concept is abstraction, the idea that you can assemble software code into chunk meaningful enough that it can be shared and reused in many different area with in company's business process.
The benefits of SOA comes at two levels:
1. At the tactical level this includes
- Software Reuse : As the bundle of code that constitutes a service can be reused.
- Increased Productivity : Because of reuse service, that simply reduce number of man-has in development , this makes a faster deployment.
- This Increase agility
2.At strategic Level, effective SOA adoption means better Alignment with the business : As this gives a big picture of all the business processes and flow.With this all kind of people(technical or funcational ) can visualize, for the first time , how there businesses are constructed in term of Technology.This will surly appreciated by business people for supporting IT projects.
Read this case study@OTN 
Invoice Processing in a Service-Oriented Environment 
by Ronald van Luttikhuizen