I love my Advantium by GE. It fit in the slot of my built-in microwave.
It acts as a microwave AND a second oven. It cooks with light, microwaves and convection. There are two different powers you can get. The high powered one (the one I have) cooks up to 8 times faster than a conventional oven. It is small for an oven - the size of a microwave. It doesn't require pre-heating which is huge. Chicken nuggets for 2 take less than 4 minutes from frozen to on the table. Since it cooks like a real oven they are crispy not rubbery like stuff from the microwave. It also has regular microwave buttons so you can use it in a traditional microwave way too.
The price will give you a heart attack but it really has been a huge time saver for us. We cook nuggets, fish sticks, french fries, rolls, casseroles . . . so much more frequently now . . . even for lunch because it's as fast as a microwave but with oven quality output.