Google's error correction seems to be getting more and more sophisticated. It still suggests alternative spellings occasionally. But where there does not seem to be any ambiguity at all it goes ahead and returns results after performing the corrections automatically. Sometimes it does both.

A look at my recent server logs is instructive.

If you type "Oman insurence group" Google asks whether you meant "Oman insurance group". But it still returned a page from one of my sites on the first page. Insurance Oman Middle East although the word "insurance" was not misspelled anywhere on the site.

Similarly if you type "martial art training center Pune" it returns the appropriate page Martial Arts India Asia although the page uses the form "centre" not "center".

Type "amusementparks united states" and it automatically realised that it should be "amusement parks united states" and returned the appropriate page.

Yahoo's spelling correction is just as good. But the quality of the results it returns is not so good.

For some incorrect spellings Google outclasses everyone else. If you type "Ibn Khaldoun school" it returns www.ikns.edu.bh as the first entry although the school is actually Ibn Khuldoon School. Yahoo does not return the url at all.