There is a great deal of help in the Domino Designer Help.
This includes a section that is dedicated to Web Design.
Remember, Domino Notes databases are already Web enabled. They just need some tweaking to make them more user friendly.
There also lots of articles here, in LotusAdvisor, IBM LDD Developer Works, the View, IBM Sandbox and more. Finally there are free on-line Red Books on IBM formerly Notes.net.
Also, on TLCC.com, there are free courses on using Domino Designer and xPages. See the “Try a Free Course” section.