infinitemac.org
InfiniteMac is a web-based collection of classic Macintosh and NeXT system releases. It allows users to run selected versions of System Software, Mac OS, A/UX, Mac OS X, or NeXTStep in a virtual machine within a browser. An "Infinite HD" disk with era-appropriate software is available. Users can customize machine and disk choices, and on some systems import/export files and mount virtual CD-ROMs.