These sites offer references and guides to JavaScript as a language in general, rather than jQuery in particular.
This site has a comprehensive JavaScript reference, a guide to programming with JavaScript, links to helpful tools, and more:
While focused primarily on its own browser platform, Opera's site for web developers includes a number of useful articles on JavaScript:
The Microsoft Developer Network JScript Reference provides descriptions of the full set of functions, objects, and so on. It's especially helpful for understanding Microsoft's implementation of the ECMAScript standard in Internet Explorer:
http://msdn.microsoft.com/en-us/library/x85xxsf4(VS.71).aspx
Peter-Paul Koch's Quirksmode site is a terrific resource for understanding differences in the way browsers implement various JavaScript functions, as well as many CSS properties: