Hi ... you. Actually I don't know if I should call you gudim or gudi.
The rich: tags and a4j: tags are quite a bit different. The rich: tags provide GUI widgets like a calendar, menues, a pick list, suggestion boxes, modal dialogs, etc. The a4j: tags are involved with capturing events, creating AJAX requests, and rendering AJAX responses. There's really not much overlap between the two tag sets.
For links, I have the
JBoss RichFaces Developer's Reference bookmarked, and I refer to it often. I also have the book "Practical RichFaces" by Max Katz, but I don't find that as useful as the online documentation. You can also Google for the Exadel RichFaces Demo pages, which show you some of the tags in action. I believe you have to register for the site, but it's free.
Greg