I'm currently on a LifeRay Portal project. We are helping our customer to develop a Sales Commissioning Portal utilizing social-network medium.
Those who develops Portal, especially Java-driven portal, will need to be familiar with a lot of JSRs ( Java Specification Request ).
The more commonly references are:
JSR 286 is an enhancement to JSR 168. Both defines Portlet Specification. There is a good read - a detailed writeup of the differences.