Portable kitchen islands can be constructed out of kitchen base cabinets with a hidden plywood and wood frame inserted in the base area. Then simply panel the sides that normally would be hidden from view if they were to be installed against a wall.
However I would be very careful constructing a portable island. The primary reason is safety. If the island has the ability to move about you risk injury if you decide to use this as a baking table with mixer or with any kitchen appliance that is required to be plugged in. Draping the cords of appliances across between an island to the wall outlet is dangerous and risk injury should a small child reach up and pull the cord or if an adult walks by and hitting the electrical cord if they did not see it.
Building codes require all islands to be fastened down to the floor with a hard wired outlet attached somewhere on the island just for this very same issue.
You can ,however,add a rolling cart for 'storage' or' prep area'... Hometalk has shown me LOTS of neat ideas...just start by typing in a subject,i.e. kitchen storage or something and read away..and don't forget to check out the margins for questions from others,& scroll all the way down to related posts at bottom...Sometimes you'll find ideas there...I love it,and it's FREE!
I have also seen where an old dresser has been used for an island by adding wheels. You want to assure that you have wheels that can be locked into place. Don't want any accidents!!
Sideboards with cupboards and drawers have lots of character. Make sure the legs can be cut down to get the right height.
I've seen people make them out of dressers, base cabinets and just plumbing pipe and boards. There so many ideas out there. I'd purchase the locking wheels though.
I found an old dresser at a flea market several years ago and turned it into a rolling island. I cut a shelf to match the top (mine has a concave curve) and attached it to the bottom of the legs with heavy casters underneath each leg. I added bead board to the back since it was unfinished and had a glass shop cut a piece of 1/4" glass to go on the top. I painted it black and put on new hardware. The addition of the casters and shelf on the bottom raised it up to counter height. Looks nice and is very functional.
Great ideas...along the line of my thinking. Thanks!
Go to Kreg Company and get free plans for cabinets. I built my granddaughter's cabinets for less than one can buy a corner cabinet. The island was the easiest.
@Anne Willer there are lots of ideas on here. One that sticks out in my mind is by @Color It Simple http://www.hometalk.com/943597/kitchen-island-before-amp-after Very imaginative and unique. As for roller wheels I am not sure that is needed with what is on the market today to help furniture move easily and not harm the floors. This idea can also be used for an old buffet and repurpose it for the kitchen. It can add a lot of character to the room.You will have to let us know what you do and update with a pic.Thanks for posting.
I used an old office desk. Worked great, added doors where the space for a chair was and had access from both sides for a set of deep shelves on the 'work' side and a set of narrower shelves on the 'coffee drinking' side. The desk had drawers on either end, and it was easy to put small (locking) castors on it. If you like the industrial look you can get a very inexpensive piece of sheet metal formed to cover the top (furnace duct-work type metal).