In almost all organsiations running SAP and Microsoft this is one of the most discussed topics : integration / interoperability of SAP (Portal) and MOSS 2007.
The attached zipfile contains a flash movie explaining all the ins and outs. Very helpfull.
This overview animation explains options and possibilities as well as limitations in the combination of SharePoint 2007 and SAP NetWeaver.
Download: SAP MOSS Interop Animation ZIP
That animation is really well done, very good explained and gives an perfect overview!
If someone is looking for the mentioned front-end integration (Sharepint WebParts –> SAP Portal, embedded), btexx has an out of the box solution.
http://www.btexx.com/software/MOSSintegrator/range-of-features.html
The new btexx MOSS Integrator makes it possible to “cut out” any MOSS content you need and use it within the SAP Portal without restricting its functionality in any way. The SharePoint Collaboration Solution from Microsoft delivers a wide range of software components that effectively enhance the SAP Portal, e.g. complete Team Sites, Wikis, Blogs, Team Calendars, Document Workspaces, Image Galleries, Search Centers and Surveys.
MOSS Integration of SharePoint content occurs via special iViews directly via the SAP Portal Content Directory (PCD). An administrator or an expert user can create iViews here and assign portal roles. btexx has developed a special wizard for the different MOSS iViews that is also useful for expert users.