Do you need a type attribute at all? If you're using HTML5, no. Otherwise, yes. HTML 4.01 and XHTML 1.0 specifies the type attribute as required while HTML5 has it as optional, defaulting to text/javascript. HTML5 is now widely implemented, so if you use the HTML5 doctype, <script>...</script> is valid and a good choice.

As to what should go in the type attribute, the MIME type application/javascript registered in 2006 is intended to replace text/javascript and is supported by current versions of all the major browsers (including Internet Explorer 9). A quote from the relevant RFC:

This document thus defines text/javascript and text/ecmascript but marks them as obsolete. Use of experimental and unregistered media types, as listed in part above, is discouraged. The media types,

  * application/javascript

  * application/ecmascript

which are also defined in this document, are intended for common use and should be used instead.

However, IE up to and including version 8 doesn't execute script inside a <script> element with a type attribute of either application/javascript or application/ecmascript, so if you need to support old IE, you're stuck with text/javascript.