There are 3 interesting project:
1-AmigaOne the official new Amiga capable to rune the newest AmigaOS (version 4.0, ppc antive), the only official solution.
2-Pegasos, an Amiga inspired computer taht runs MorphOS with highly 3.x amiga campatibility, fast and prosmising os.
3-There is also a ColdFire project, an accelerator card (ColdFusion) that add to the Classic Amiga (the old models) a Motorola ColdFire processor (the 68k evolution), and can accellerate the classic software a lot.