ROM Emulators for OLPC
A ROM emulator speeds up firmware development. You can try out new firmware builds by downloading over a cable, instead of having to reprogram a FLASH part every time.
For OLPC work, you need an emulator that supports the LPC/FWH interface. LPC stands for Low Pin Count, FWH for FirmWare Hub. They are minor variations on an Intel-defined interface to FLASH devices, which uses fewer signal wires than the older JEDEC interface. The slight difference between LPC and FWH is unimportant here; emulators that can handle one can handle the other.
PROMjet
The Emutec PROMjet works well with the OLPC development board. You also need the FWH/LPC option and a PLCC adapter. The part numbers are PJ-8M-85, OPT-LPC, and ADP-32PLCC-LPC. The total price is about $1300.
That configuration downloads from Windows over USB 2.0, very quickly. If you want to download from Linux, you'll also need the Ethernet adapter - ADP-LAN. I don't know the price for that option.
Everything is in one compact package, about the size of a mobile phone.
PROMice
The PromICE with LPC Memory Emulator will probably work too.
It downloads via a parallel printer cable or a serial cable, from either Windows or Linux. I have had good results with PROMice in the past, but I haven't tried the LPC Memory Emulator add-on, so I can't vouch for it. The parallel-port download speed is not nearly as fast as the PROMjet's USB 2.0 downwload, but it still beats having to reprogram a FLASH chip every time. The total price is $2375 (ouch!).
It's two boxes, each about the size of a paperback book.
WICE
The WICE-8MA/FWH looks like it would work, but I don't have experience with it. Windows via parallel port.
Artec LPC USB Dongle
Artec Groups LPC dongle should also work. At the moment there isn't PLCC cable available (yet), but it can be made. Supports LPC FWH and LPC Memory interface. As an additional bonus there is post code display and post code forwarder to serial console. There are also 4 separate jumper selectable images, each 4 MB large. Programming 4 MB image takes approximately 50 seconds over USB cable on Linux. All the software and hardware is open source (including schematic). Works on Windows, Linux and CVS version at opencores.org also supports OSX.
Price 150 EUR.
http://www.opencores.org/projects.cgi/web/usb_dongle_fpga/overview
http://www.artecgroup.com/products/hardware-products/programmable-lpc-dongle.html
Short tutorial by coreboot people: