There are several commercial products (SSL VPNs) which do this, and the most popular is one called Netilla, which runs off of a hacked Mandrake. This can be used to provide IP tunneling over SSL via a series of Java applets, and works on Windows and OS X (with the latest Java patch). They want a lot of money to turn this functionality on for you, however.
It would not be too terribly difficult for someone to embed a SSH Java Applet into a page to produce the desired functionality with authpf, as there are several such programs available. Whether it's secure or not is another story, but it can be done.