There are a few things you can read up on or work with now.
IBM WebSphere portal is bilt on JetSpeed from apache,
you can download it and check it out here,
You may also want to check out IBM's developer sites,
WebSphere Developers domain and VisualAge Developers
Domain , here http://www7b.boulder.ibm.com/wsdd
and here http://www.ibm.com/vadd
aswell as http://www.ibm.com/java
And last but not least this is IBM's WebSphere Protal
products page, you can get some good information from
here also http://www-3.ibm.com/software/info1/websphere/index.jsp?tab=landings/portalsplash
PS: Search http://www.redbooks.ibm.com
/ to find a lot of
online material in the form of IBM red books,pappers, etc..