I use Ask mostly, because it is the only search which is both having big index and relatively spam-free (where else can you see viagra.com as #1 for 'viagra'?). Also, Google for professional purposes.
Google - i dont really use yahoo or windows live atall. well i cant remember the last time i used them actually.
Do you guys use Baidu because it is more relevant of because it is a Chinese search engine? How good are the search results of Baidu... do you think it has technology to compete with Google internationally? Of course I always use Google .