What is JSR-168 and WSRP?
JSR-168 (268 in draft) is a Java-based standard for how to code pluggable Portlets (i.e., SharePoint Web Parts) that interact with Java-based portals. Because SharePoint is a .NET-based Portal Framework it does not support JSR-168. SharePoint supports the WSRP (Web Services for Remote Portlets) standard.
WSRP is an interoperability standard and a language-neutral way to request and transmit web service data. Microsoft supports services orientated architectures (SOA) and web services interoperability, by adhering to a complete set of web service specifications.
Both Portlets and Web Parts have the potential to support WSRP.
Why do I even bring this up? If a customer has a Java Based Portal then JSR-168 may be a good standard for them to adopt. Unfortunately, some customers still have the impression that because SharePoint isn't JSR-168 compliant that it lacks some universal standard, which in fact is not correct. SharePoint supports WSRP and WSRP could be consumed by both portlets and web parts (genuine interoperability).
The bottom line is that Microsoft is committed to the utilization and support of open, standard technologies and protocols. We can see this today in SharePoint's adoption of LDAP and Kerberos in addition of AD. The world is moving towards XML as a standard document and data format with SOA Architectures for application integration. With web services SharePoint can communicate with Oracle Apps, Banner, SAP, Blackboard, etc... WSRP provides a standard for this communication.
Customers evaluating portal products are bombarded with decisions and often misinformation. SharePoint is much more than a portal that contains web parts (portlets). The underlying services are as important, or more important, than the web parts themselves. The BDC, Excel Services, Forms Server, Web Services, Office Integration are just examples of how services raised the bar and make product like SharePoint much more than a portal.
Lastly, some customers have asked about JSR-268. Both JSR-268 and WSRP 2.0 are in DRAFT. It is unlikely that any enterprise software vendor can commit to supporting these in 2008. Or, that any enterprise architect can require their support for a standard that does not yet exist.
Additional Resources
Wikipedia "WSRP" - http://en.wikipedia.org/wiki/Web_Services_for_Remote_Portlets