The machines will be aimed at organisations running operations where a fully fledged PC is not needed, said Jonathan Schwartz, Sun's executive vice-president of software.
Due out some time next year, the systems will run open source programs including Linux, the Mozilla Web browser, the OpenOffice productivity suite, and Evolution, an open source e-mail program.
They will also use Java smartcards, allowing users to log securely into any available machine in an office or classroom and load their personal settings onto that system.
"We think we can give you a price that's half the cost [of a Windows PC] at acquisition," said Scott McNealy, Sun's chief executive. He described the initial market for the machines as "compelling, if limited".
The desktops also ship with the open-source WINE (Windows Emulator) program, allowing them to run Windows applications, said Tony Siress, senior director of marketing for Sun's desktop software division. They will also include the Samba program, providing access to networked file and print services.
Sun executives positioned the systems as a way to free users from Microsoft's grip on the desktop, but one analyst wondered why businesses would buy the systems from Sun, rather than buying generic "white box" systems and loading the open-source software onto the machines themselves.
"Sun's value-add appears to come from the smartcard," said Pia Rieppo, a principal analyst for the workstation market with research company Gartner. "It says it can offer secure systems that allow users to carry their identity around with them. But I'm not sure if security will be enough to make companies buy a PC from Sun."
Sun aims to offer the systems as part of broader packages that also include its servers and other products.
A typical package will include 100 of the Linux PCs along with a small server running Sun's portal and identity server software, said Sun's Schwartz.
The systems on average will cost companies $49 (£32) per month per user, compared with about $170 (£110) per user per month for a typical Windows PC, Schwartz claimed. Over a period of five years users would end up paying 30% of the amount they pay for Windows PCs, he added.
Sun is not the first vendor to offer Linux on the desktop. Dell offered Linux PCs for a while, but pulled the plug citing lack of interest.