OS-9/6809 runs on a variety of platforms, perhaps the most (in)famous being the Tandy Color Computer. Other systems include the SWTPC SCB-69, the Gimix 6809, Smoke Signal Broadcasting's Chieftain 6809, FHL's TC-9, the Febe, and a host of others, most of which are SS-50 bus machines. Note that OS-9/6809 is no longer supported by Microware, but many user groups, BBSes, and a handful of FTP sites offer help and maintain software collections for OS-9/6809.
OS-9/68K runs on all 68XXX family CPU's
OS-9/OS-9000 runs on Most PPC, ARMv5 and ARMv7-A, X86 Pentium class or better, SH4/SH4a, and other CPU's.