Originally upload at www.thingiverse.com/thing:14421Decemnber 8th 2011.
Updated and improved some things to better attach to the ultimaker. Works now with 100ml syringes. Still uses the filament for 'driving' the syringe. Also new are the end stop enlargers so the endstops still work with the syringe attached. 
The concept is more or less the other way round. The filament pulls the syringe and squeeze the material out. 
for more images and movies, see http://www.facebook.com/europerminutedesign

Instructions
Resize the shapes suited for your syringe. 
Print the syringe holder. 
Print the end stop enlargers. 
Screw same [ultimaker spare] m3 bolts through the holes to fixate the syringe holders to the moving head. 
Attache everything. 
Generate gcode 
Without temperature settings 
Very low extrusion speed 
Open the GCode in a text editor and replace "E" with "E-".
[we want to pull the filament not push it, you can also change the firmware, but this was easier for me] 
Increase the flow by changing the filament diameter.
Alternatively: In the GCode, you can use M302 to allow the extruder motor to turn without the nozzle being heated up.