Stainless steel has become the standard look, but you can still get your fridge in different colors — generally white or black, although you can get some random designer colors if you desire. Some models allow you to attach panels to better integrate your fridge into your cabinetry, but unless it's a complete integration, we'd suggest avoiding the 80's paneled fridge look. Stainless steel might be popular now, but so are the old tacky fridges we thought were so cool looking back in the day. Like any other purchase, it's best to go with what best suits your general kitchen aesthetic and decor.
Configurations: French Door, Side-By-Side, Top-Bottom
Generally speaking, the bigger the fridge and the more features you have, the more energy you'll be using. Most modern day fridges will beat the pants off that old fridge you keep in the garage in terms of energy efficiency, but it's still a good idea to compare models. Particularly efficient Energy Star models might qualify you for rebates and discounts from your utility company, so check before you buy, as it could help to offset your purchase cost.
A fridge is a fridge, and they generally all do a pretty good job at the basics — keeping your food cold. There are lots of options you can get with modern fridges though, some of them obvious and others well beyond the scope of traditional refrigerators. The traditional options of an ice maker and water dispenser are now pretty standard. Some fridges come with built-in replaceable filters, which is a nice alternative to a big pitcher of filtered water taking up space in your fridge and always needing to be refilled. Adjustable shelves and automatic opening trays are a nice touch. Other options include LED lighting that fades on when you open the fridge so you're not jarred awake by a blast of light during your late night fridge raid. Even fancier options include alarms that sound when the door has been open for too long. Some fridges even have USB, LCDs, internet access, and other crazy tech built in. Whatever happened to hanging up your little kids' drawings?
Hinges/Doors: Not all fridge doors open the same way. Depending on the hinge setup, the doors might swing within the fridge's frame or outside. So if your fridge is 36", it might need up to 2" more on each side if the door hinges on the outside edge. Measure the fridge with the doors open to make sure there's enough clearance for the doors to open (on both sides if you have a side by side or french door fridge). Also remember that the handles are a few inches deep as well, so if you've got your fridge sided up against a wall, cabinetry, or other obstacle, be sure to count in those extra inches so the door opens far enough that you can comfortably reach inside the fridge. Additionally you'll want to check out the total depth of the fridge with the doors closed and open. When closed, you'll need to consider how far it sticks out from your cabinets around it. When open, you'll want to ensure there's plenty of space to move around with the stuff you've just grabbed.
Water/Ice Box/Side Shelves: Lots of fridges come with water dispensers and ice boxes, but depending on where they are located inside of the fridge this may be an issue. If the ice maker is in the door itself, you'll need to be careful that you calculate that big box into your width considerations. If you've got a limited amount of space to the sides and can't open your doors all the way, that big box might be in the way of accessing and reaching into the fridge.
Counter Depth: If you'd like to put your refrigerator next to a 24" cabinet, chances are your fridge is going to stick out quite a bit. Counter depth fridges are a bit deceiving in that they're not all exactly the same depth as your counters, but they come quite a bit closer than a full size 34" or so refrigerator. A 26" deep fridge will get you much closer, and after a week you won't even notice the depth difference,
Full size refrigerators can run you anywhere from a a few hundred dollars on the low end to thousands upon thousands of dollars for a professional grade refrigerator (think Sub Zero, Viking, or similar brands). Just under $1,500 will get you an excellent fridge, and any more than that becomes a matter of features and specific requirements. $2,000 plus gets you most of the bells and whistles, and any more than that you're looking at higher end models. Many manufacturers or stores will package appliances together for deeper discounts or offer promotions once in a while. Again, keep an eye out for utility company rebates for energy efficiency.
You can't go wrong with most modern refrigerators — just make sure it fits and you should be content, particularly with a well stocked fridge full of non-spoiled food. Happy eating!