Wouter has released a great series of articles about Service Applications in SP2010
http://blogs.code-counsel.net/Wouter/Lists/Posts/Post.aspx?ID=149
Following these articles you’ll learn how to build a SharePoint 2010 service application and how you can construct them with different connection and provisioning techniques.
Wes is the Principal Solutions Architect at Content and Code in the UK. He's currently working on several SP2013 collaboration platforms and the CKSDev Visual Studio tools. 
