Inverter

Cobra CPI 2575 2500 Watt 12 Volt DC to 120 Volt AC Power Inverter
$299.95
This is my second try with this inverter and the second one I am returning to Amazon. Regardless of your battery bank and regardless of the cables used, this product is pretty much worthless for one reason. That reason being the Low voltage alarm. On this product it comes on as early as 11.7 volts which is totally unacceptable. 11.7 volts is way to early to be setting off alarms. At that voltage you still have A TON of battery life left before you should even be concerned. The threshold for the alarm is 11.3 +/- 3% which max is 11.669 volts. Both of the inverters I had were on the high end of that scale. The first setup was connected to 3 brand new deep cycle Interstate batteries with 4, 18" long 4 gauge cables running to the inverter (Overkill if anything). The second try was 2 brand new deep cycle 6 volt golf cart batteries with 4, 30" long cables running to the inverter. After the first day of camping the batteries have already drained off into the mid 11 volts and these inverters start sounding alarms and don't stop beeping until you turn them off. The industry standard for low voltage alarms on inverters seems to be 10.5 +/- .5 volts which max would be 11 volts and that is a lot better then 11.7. I returned this inverter and I am purchasing a Vector brand inverter with the best alarm threshold with a max of 10.6 volts before the alarm sounds. However, when these inverters are getting the volts they need with the heavy cables they need they do put out the advertised 2500 watts no problem. Amazon's return policy is amazing by the way.

Update 2/17/10....The Vector inverter even though advertised as 10.6 max for the alarm started sounding it's alarm at 10.97 volts. That inverter was not much better then the Cobra in any aspect but it was a lot more money. So my final verdict is that these are good inverters for a great price with the only downfall being the low voltage alarm coming on way too early.

Duracell DC to AC Pocket Power Source Inverter 175 Watt #813-0291-07
$39.99
The product is smaller than I thought it would be but it can power my laptop and cellphone. It works great so far except for noticeable noise upon powering on (it might have an internal fan). The on/off button helps instead of pulling the plug and dropping something that might cause an accident when you're driving.

Xantrex Technologies 851-0400 XPower Plus 400-Watt Inverter
$59.99
works as advertised it does what is is supposed to do for the price, you can hear the fan, but with an music or tv it is not noticeable, low battery auto shut off works very fast

Jensen JP30 300 Watt Power Inverter
$79.99
Bought this to plug my laptop in while travelling for the kiddos to watch movies (cheaper than an in-car video system). I also plug in a set of computer speakers because the ones in my laptop are not loud enough. I only have good things to say about this inverter...and that is a really good thing because I have tried about 6 others that all wound up being returned to the store (and they costed WAY more than this one). I have no problems with it getting hot, making any loud fan noises, or beeping when it shouldn't. Others have written bad reviews saying it wouldn't stop making a beeping/buzzing noise, which caused them to either return it or stop using it, but they must not have read the instructions. This thing beeps/buzzes for a reason...it is a warning to let you know that either something drawing too much power is plugged in, or it is unable to draw enough power from your battery (meaning your battery is about to go dead, or if the car isn't running, which means your alternator isn't constantly recharging it reducing the amount of power it kicks out). Whatever the situation is, it doesn't just beep/buzz for no reason.
My one and only complaint about this inverter how far the outlets are spaced apart...an extra inch between would have been great because I have to use an extension cord to plug the speakers in (can't fit 2 things plugged in if one of them has a chunky adapter). This isn't a problem specific to this inverter though, of the many I have tried and returned, almost all of them had the same issue. Other than that, this thing is great for my needs and many others I can think of. It has a nice solid build feeling to it so I don't fear it getting cracked if dropped on the ground or anything like that. I have only had it a few weeks, so I can't speak of it's long-term use durability...but for less than thirty bucks, I'm fine if it only lasts a year.