I have a propane cook stove so when the power goes out I can still use it to cook on. The new stoves do have a electric starter in the oven so if no power you can't use the oven, you can use the top burners you just have to light them with a match.
Bar B Q grill, The one draw back to this is you need propane to use it. In a short term emergency this would be ok.
Camp stoves also works great for short term use just be sure to have extra fuel stored for it.
Solar oven, rocket stove, or a wonder oven are all other options. You can make your own wonder oven, rocket stove, and solar oven, there's lots of patterns on the internet.
I have a solar oven that I haven't had or taken the time to use so I am hoping to start using that soon so I can share some recipes for it.
I also have a Thermal cooker which I love, I've only used it a few times but look forward to using it a lot more. I got it here at Saratogia jacks This is great because you can fill it in the morning and just take it with you where ever you are going. It also has two pans so you can cook two different things at the same time. You have to heat it up real good, then you put it in the cooker and just let it sit and cook. It is the pretty much the same concept as the wonder oven and hay bale cooking but this is portable.
Then there is the old fashion cooking over a open fire. You do need a place and extra wood to do this. There is a lot of information on Dutch oven cooking on the web also.
Which ever one you pick and want to use be sure to practice it so if you need to use it you know what you are doing and if possible have more then one way to cook.
If you have any other options please share them.
What is you preferred alternative cooking sources ?