Yep, Watch your power needs when buying those things like FP said.
Those little ones like that are often expensive because they may be Pure Sinewave types. That would be more like real grid power. But the smaller ones like those are also seldom very many watts.
Something like this may be allot better deal and should run about anything fine though it's most likely a Modified Sinewave inverter.
http://www.donrowe.com/inverters/cobra_400.html
That is $34 for 400watts continuous! You should be fine running it from a cigarette lighter plug or you can do a simple easy hard wire direct to a battery.
Should run the laptop fine, also charge your cell phone, and if you have a flat tire late at night in the dark in a heavy wooded area it will also run a 100watt house lamp for you to change the tire while you listen to the coyote's howl very nearby! Don't ask how I know the lamp and tire change part LOL
I use small ones like that allot, though the one I linked looks better than what I actually have. Mine are older because I have used them for years.
Wal-mart sells something like that type I listed. Also another couple things to think about with these is some vehicles have a hard to access lighter plug, so you may not always be able to use the little types that plug directly in. I have several vehicles those would not fit if I had one. The Jeep with a 5speed I dought one would even plug in and if it did it would be in the way and I couldn't use it anyway while driving. I think same problem with the Cougar and Lebaron with floor shift automatics the way the lighter is set up near the shifter.
The bigger ones with the plug on the cable and just sit inverter in floor work in about any vehicle.
Other thing is always get bigger than you need. You never know when you might want to run something else also later. Maybe a portable DVD player?
It's nice to have those like I linked around too. Though I have several LARGE ones and BIG UPS Matrix 5000 and SU 2200 rack mount to run half my house and several computers, it was still nice to have a little 450watt inverter when we were without power for about 2 weeks for that big ice storm.
I use the 450watt one for allot of things and they can be fun to have around and very useful.
For nearly same costs I'd go with the larger one, that little direct plug in type may be prettier and use a little less space, but not nearly as userful!