This depends on what you have (especially on the entitlement side) and what you want to integrate...
In general it's possible for CRM functionality (which I have tested so far) accessed via a SAP Netweaver WebAS (through Java and ABAP stack), but first you have to think about SSO (jBoss portal users <-> SAP-Users).
I understand this post is very old. However, I am doing the same research. Basically we are evaluation portal product for our company. And one of the biggest criteria is ease of integration with SAP system we have here. Any information from your experience will be very helpful.