Justin Maynard suggested CoolTerm as a freeware MAC/OSX serial terminal option. ZTerm seems to be the other favorite.

CoolTerm has versions for OSX and Windows. We tried the Windows version, the settings that worked for us are shown above. Be sure to check handle backspace character, and change the enter key emulation to CR. As of firmware 2.3 the Bus Pirate never uses flow control, and it may cause problems with some terminals.