Some really good information on SAP and MOSS Integration available at the following post:
http://blogs.msdn.com/joanna_bichsel/archive/2007/09/25/sap-integration-with-moss.aspx. and the following link on MS Site: http://www.microsoft.com/isv/sap/technology/interop/sharepoint.aspx.
Apart from this MOSS Out Of Box have iView webpart which allows users to connect to SAP EP from MOSS. If you are considering using SAP Data in MOSS for Search etc consider using Business Data Catalogue. With the help of BDC you can crawl and index SAP DB (through web service if you like) and create a MetaData Database in MOSS. This data can then be used in MOSS Search results (customie the CustomResult.aspx page with XSLT formatting and use thepower of Math, Logic of XSLT using SharePoint Designer) or use OOB web Parts like Business Data List to allow users to filter through the SAP Data. You can implement security on the Application Definition File so that users can access the data that is meant for them. The best part is when using Business Data List, when the users can filter the data on the MOSS Page directly and get required information (it adds the AND or OR SQL Clause in the query on runtime) which was almost impossible without BDC.
This posting is provided "AS IS" with no warranties, and confers no rights.