We have a GoPower 300 watt pure sine wave inverter:
Inverter installed! | Flickr - Photo Sharing!
I bought it from Amazon.com
Go Power! GP-SW300-12 300-Watt Pure Sine Wave Inverter : Amazon.com : Automotive
I installed it myself and this was not difficult. It is recommended to install an inline fuse. I used a 40 amp ANL fuse and fuse holder. This inverter can use a remote power on/off switch which I recommend you do, since the inverter will otherwise have a drain on the battery even when there is no load.
The cables supplied with the inverter are short, and you need to install it as close to the battery as possible although not in the same compartment.
Let me know if you need more information.