Atmel Flashing Tool from HobbyKing

Hmm, this could open up quite a few possibilities.  It's a device that presses down over an Atmel microcontroller and makes the proper connections to flash new firmware.  No soldering onto pads!  Looks perfect for flashing ESCs.  You'll need the USBasp device as well.

Atmel Atmega Socket Firmware Flashing Tool
USBasp AVR Programming Device
eXtreme Burner AVR software

HK describes it thusly:

This genius tool makes flashing the Atmel Atmega MCU found in many ESCs or other devices using Atmega processors a walk in the park. No need to solder or create cumbersome clip on devices, simply connect the socket flashing tool to a USBasp AVR device and place the socket over the exposed Atmel MCU! 

Requires: USBasp AVR Programming Device for ATMEL proccessors.  Suits the Following MCU: Atmel Atmega8, Atmega48, Atmega88, Atmega168, Atmega328

• Fits Atmel processors that use the "QFP32" package.
• Doesn't fit AtMega64 used in Turnigy 9x.
• Doesn't work for SiLabs processors.

Here's a video where hummingbirdRPV flashes four ESC's without even removing them from his quad.