According to this press release, O'Reilly is partnering with Wolfram Research to create a Web 2.0 version of Mathematica that will "be browser accessible and, utilizing AJAX technologies, will emulate the desktop version of the software with remarkable fidelity". I'll be very interested to see how they handle equations (MathML isn't well supported) and grahpics (IE7 doesn't do SVG, so what, Flash? Silverlight?).