Waterfall 2006 - International Conference on Sequential Development
At first, I thought it was serious - but this site is almost as good as the Curt Jester.
Waterfall methodologies are those that progress in linear fashion through a series of stages - for example, Feasibility, Requirements, External Design, Program Specifications, Coding, Testing, Production.
The problem with waterfall methodologies is that they don't work all that well. Trying to create complete, perfect system specifications before you start any coding simply ensures you've wasted a bunch of effort, because once developers start coding, design flaws become evident and require that you revisit earlier stages.
Except that you can't, because that stage is complete and there's no budget for going back.