Resources to integration with external web service at desktop level

I am using ESRI based GIS software, I looking a way to integrate ESRI solutions with external web service of other information system (CRM,ERP) and to develop custom applications for the collection, conversion, maintenance, and analysis of data. Mainly visualization of external data in maps when data is streamed online

1. is it possible with out ArcGIS Server ? I'm using version 10.1 Advance level

2.Where can i find resources to integrate GIS to external web service at desktop level ? I have no idea on where to start and to proceed further.

3.What ArcMap Tools and Commands host the trigger for calling the services ?