Hi Rich, I am using an IAR rebranded version of the Segger J-Link (http://www.segger.com/cms/jlink.html) that came with an IAR dev board that I am borrowing. I have not tried anything else, so I can not recommend any on basis of my own experience. If I would buy one I would maybe look at the ARM-USB-TINY-H or ARM-USB-OCD from http://www.olimex.com. It would be important for me that it works well with openocd and other open-source tools, and without any restrictions (like the Segger EDU version has).
Olimex also has a minimal dev board, but I guess buying a LeafLabs Maple (http://leaflabs.com/devices/maple/) would make more sense, since it has excellent open-source support and a community around it. Futurlec also sells a cheap STM32 board.