What's it cost?
Freestanding worktables or rolling carts can be had for as little as $200. Basic built-in islands made with stock cabinetry and butcher-block or stainless-steel counters start at about $600. More features, larger sizes, and costly materials can easily push the price above $5,000.
DIY or hire a pro?
Anyone can put in a worktable or cart. An island assembled from cabinetry is more of a challenge but doable for handy homeowners. Call in the pros for custom configurations if you plan to have plumbing fixtures and electric appliances or if you want a stone countertop (shown).
An island ought to have enough counter space to meet your needs, look proportional within the kitchen, and have ample pathways around its perimeter. For smaller kitchens, a worktable or rolling cart may be a better choice than a built-in.