Besides using a stub for console.log and alert()s in many simple debugging cases, i also use:
Microsoft script debugger - general debugger. will work fine with non-minified source code. must be enabled in advanced options of IE http://www.microsoft.com/Downloads/details.aspx?familyid=2F465BE0-94FD-4569-B3C4-DFFDF19CCD99&displaylang=en DP_Debug - print out complex variables in a seperate window http://www.depressedpress.com/Content/Development/JavaScript/Extensions/DP_DeBug/Index.cfm
