MHTML (MIME HTML), a web page archive format introduced with Internet Explorer 5 and used to combine various images, animations along with the source code into a single (.mht) file, will be supported by the upcoming Google Chrome 14 release.

In fact, as of June 13th, Canary Chrome and WebKit builds already include such feature.

According to Wikipedia, MHTML file format is already supported by a few web browsers, including:

Internet Explorer 5-9 (IE8-9 saves web pages in MHTML format by default),
Opera 9-11 (MHTML as the default saving format was introduced in Opera 9.5),
Firefox 3 (no native support, extension is required).

So here you have it, 12 years after the initial IE5 release, it looks like Firefox remains the only web browser that does not support this feature right out of the box.

[Thanks, Blake]