One of the recent trends is to create a project wiki when a project starts and keep all documentation, tips and tricks in there from day one. For our projects we always use XWIKI (http://enterprise.xwiki.org/).
It's simple to set up, you can use it within an OAS or OC4J but also standalone.
But with all Wiki's, Blogs or any other form of documentation, if it's not maintained / up to date people won't use it .....
Till Next Time
