If you've done a regular search for API reference documentation, most likely you've come across links to very old versions of the API (e.g. links to Java 1.4.2 instead of Java 5 or Java 6), or you've probably come across plenty of links that are completely unrelated to the actual search (getting links about fabric when searching for "Thread"). This is why I have created a Google Custom Search engine specifically for searching through language and library API reference documentation. In addition, I have created an extension for Google Chrome and an OpenSearch plugin that works in Firefox and Internet Explorer that simplify the use of this custom search engine.
If I've piqued your interest, then please take a look at:Development and Coding Search: Search Engine for Programmers, Developers, Coders, and Software Engineers