IBM WebSphere software is an "integration and application infrastructure software" that can interoperate with SAP NetWeaver components like Portal and Exchange Infrastructure.
Interoperability of SAP Netweaver and IBM WebSphere
The interoperability of SAP NetWeaver and IBM WebSphere enables a higher degree of integration of heterogenous business systems in the IT environment and helps preserve existing customer investments.
How to Interoperate SAP Enterprise Portal and IBM WebSphere Portal Server
This guide describes how the IBM WebSphere Portal Server (WPS) and the SAP Enterprise Portal (SAP EP) can interoperate. Starting with SAP Enterprise Portal SP Stack 13, you can integrate the two portals by either displaying SAP EP content within WPS (with the help of WPS's Web Page Portlet) or WPS content in SAP EP (with the help of SAP EP's URL iView).
More on IBM WebSphere Interoperability
WebSphere Business Integration for SAP (IBM Redbook)
How to Set Up Single Sign-On Between an IBM WebSphere Portal and the SAP Enterprise Portal Using JAAS
This guide provides instructions for setting up a single sign-on (SSO) scenario using an IBM WebSphere Portal (WSP) as the leading portal accessing an SAP Enterprise Portal (SAP EP). After launching SAP EP from WSP, you can log on to SAP EP with the same user that is already logged on to the WSP.
How to Set Up SSO Between SAP NetWeaver Portal and IBM WebSphere Portal Using TAI
The following article provides steps to guide you through the installation of a custom Trust Association Interceptor (TAI) module for single sign-on (SSO) between an SAP Enterprise Portal (SAP EP) and an IBM WebSphere Portal (WSP).
Interoperability of SAP XI 2.0 and WebSphere Business Integration 4.2
The purpose of this Quick Guide is to describe the configuration steps required to set up interoperability between SAP Exchange Infrastructure 2.0 and IBM WebSphere Business Integration System (IBM WBI) 4.2.x using the WebSphere Business Integration Adapter for SAP Exchange Infrastructure V 1.0 (aka WBI Adapterfor SAP XI) and the InterChange Server as an Integration Broker.