Liferay and JBoss are among the few popular open source poral servers. Here is another comparison between them by InfoWorld -
JBoss vrs. Liferay
About IBM WebSphere Portal, Liferay Portal and other Java Portals, JSR 168 portlet, JSR 286 portlet, portlet development, and WSRP etc. Will also try to write about mobile application development like iPhone development, Android development, Nokia development etc.