Over at Top10Disney.com there's a great list of 10 unbuilt Disney attractions. Her3's one of the 10 but you can read the entire list at
here.
WestCOT
Planned as an Epcot style park for the west coast, WestCOT was to be built on the area that was the Disneyland parking lot and is now Disney’s California Adventure. With guests visiting Walt Disney World in Orlando for several days – or even a week, Michael Eisner wanted to keep guests at Disneyland for more than one day. The answer was to build a second park and he challenged the Imagineers to “wow” him. The result was a three billion dollar park, WestCOT. However, following the dismal financial performance of the opening of EuroDisney (now Disneyland Paris), Michael Eisner was weary of investing such a large sum of money. Instead he had plans drawn up for a less-expensive option for a second park, and Disney’s California Adventure was born.