What are the safest temperatures to heat different filaments to? I recently backed a 3D printer on Kickstarter, and I would like to 3D print parts for high-temperature applications. So I have two questions; 


What's the highest temperature polycarbonate can be safely heated to without warping or releasing toxins?
If there's a filament with better temp-resistance I can print could you tell me? (If you know the highest temperature it could reach safely, that would be helpful too.)


My 3D printer will have a heated bed up to 100°C, and an extruder temp of up to 250°C.
Polycarbonate is heat-resistant up to ~120C. Above this temperature it will gradually become flexible and may irreversibly bend. It will not generate any toxic fumes all the way up to ignition temperature (630C), because it's fumes are not considered harmful. Note though, that with your temperature limit you may not be able to print with polycarbonate, or only do so at a very low speed.
According to the sheets of commercially available printable plastics, PC has the highest printing temperature and heat resistance among them, seconded by nylon. This refers to the FDM printers only. SLS printers may be able to use other materials, even metals like aluminum or titanium, so if you really wish to get temperature-resistant prints, you may look for workshops that have SLS printers and ask them.