The answer really depends on what OS you're considering running. There are good emulators available from WindRiver, GreenHills, lauterbach to name a few.
Of course, since I'm a freescaler - I use our own Codewarrior debugger with the linux OS.
http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=CWS-PPC ... Paul
