Banner and button advertisements are dying a slow but painful death. Custom marketing things are growing to be by far the most powerful with the best ROI.
I loved Jim Sterne's book, "Advertising on the Web: What makes people click"...it's nearly I think 500 pages chock full of excellently-written material. It covers much of what is hot now, such as push advertising.
They're being replaced by more customized solutions and ads. For example, when you see (example) "GVU User Survey 2000 sponsored by Nike: just do it" then that's customized. If you see "GVU User Survey 2000
then it's not customized.
Of course Nike wouldn't do that because it's opbviously un-targeted.