Pop your top and lift your lid with this Z axis extension kit. I can print up to 205mm so far, and it can probably be tweaked to go higher. (Now that I have it installed I realize that I could add another 10mm to the base)
This was inspired by http://www.thingiverse.com/thing:4261 and the pulley mounted crank from that settup works great with this.
I've added .obj files for those who want to stretch things a bit more...
I found the easiest was to install was to unscrew the top of the Makerbot and lift the whole lot up. Remove the lower Z axis retainers and screw the four base towers in. The top lifters should be installed as per the top. I included a few extra screw holes in case you think you need extra bracing. Note that one of the lower parts has some print support to cut out. The top lifters are adjustable so you can raise it or lower it to the capabilities of your machine. You can also lift the Z axis pulleys to the tops of the rods to get a little extra height out.