If you begin a query with the [spell:] operator, Google will spell-check your query instead of performing it. If it notices potential misspellings, it will offer alternate queries for you to try. For instance, [spell: corect my speeling] will provide several possible spell corrections for this query.

A similar feature is applied automatically to all queries. Look for links of the form 'Did you mean: "correct my spelling"' below the search box.