gistfile1.js

// Idea from http://dbaron.org/log/20100424-any

jQuery.expr[':'].any = function(el, i, match) {
    return jQuery.find.matches(match[3], [el]).length > 0;
};

jQuery('body :any(div, form) p'); // Same as jQuery('body div p, body form p')

jQuery('div:any(.foo,.bar)'); // Same as jQuery('div.foo, div.bar')

I was thinking that it might be nice to add this to the core, but maybe drop the :any so we can use selectors like:

jQuery('body (div, form) p');

I like it, @Mottie. I prefer

jquery('body [div, form] p');

as seen in regexp

Both your suggestions would mean that jQuery's selector syntax would differ from the actual CSS syntax. It'd be best for the two to keep in sync as much as possible.

One thing you should keep in mind is that the specification currently mentions :matches instead of :any. However, as there are two independent implementations, it's likely for the specification to be updated in order to reflect that.
http://dev.w3.org/csswg/selectors4/Overview.html#matches

Good point, @beverloo. The jQuery selector syntax has helped me better understand CSS. Syntactic sugar isn't enough of a benefit to justify moving away from the standard.

A different approach — http://twitter.com/padolsey/status/119790781417537536:

$.expr[':'].matches=(function(_){return function(el,i,m){return!!_(m[3]||'*',[el])[0];};}($.find.matches)); // CSS4 :matches selector for jQ