Nelson has wirtten a fantastic post about the modern disposition of the Ultima games, including unauthorised bundles of the game's many incarnations along with easy-play emulators for running them on modern hardware.
The most impressive is the Ultima Classics collection. "Sedryn Tyros" has collected the Ultima games and distributed them in a bundle along with DOSBox setups that make it easy to run the games. His supplement also includes original pre-PC versions of the early games, often better than the PC ports, along with the emulators you need to play them on a PC. Alas, this collection is completely unauthorized and you'll have to scour your back alley's bittorrent site to find it.
Another option is fan-made reconstructions of the game engines. The best is Exult for Ultima VII, a portable engine that runs the classic game on many platforms (including Xbox!). Just take the open source game engine, copy over the assets from your Ultima Collection CD, and you're in business.
