I bought one of these at Walmart for around $15 when I couldn't find my no-name inverters. This one has worked great, I take it on every plane trip I go on. Normally I use this to power my laptop ($15 for an inverter is better than 50-100 for a laptop-specific DC power adapter, if you can even find one).
One time when the battery was low, the inverter kept shutting itself off. It would work for a few seconds, then quit until I unplugged + plugged it back in. My theory is that when the laptop battery was extremely low, the power adapter was drawing more wattage than this little inverter could handle. Other than that one time, I've had no problems. Has a little fan noise, normally not noticeable. Definitely recommended, nicer (better built) than the no-name inverters I've tried.
Black & Decker 100-Watt Inverter VEC1044BD