Just one word of caution: WebSphere Commercial Edition and WebSphere Community Edition are not really very much alike. If you want to learn WebSphere because your company or client is using the commercial edition, I'd suggest you see if you can get a copy of the commercial version WebSphere Applicatoin Server or Rational Application Developer (Which comes with WebSphere) from them. Otherwise, you can get a trial copy from the IBM website.
I might humbly suggest my own website, which is full of free tutorials and CBTs that help you perform such WebSphere tasks as deployment, configuration, clustering and installation. There's also a bunch of free multi-media tutorials on things such as configuring portal, J2EE development and the like, most of which demonstrates application development using IBM's Rational Application Developer (IRAD).