Statcounter's stats for this year so far show that Bing overtook Yahoo search in January to become the second biggest search engine.
Bing and Yahoo combined have 8.3%, Google has 90%.
and you can get more data from:
Statcounter only shows Baidu having 0.32%! Statcounter's sample looks biased: I would guess not enough China (67% share in China, according to Statcounter, has to be more than 0.32% globally).
Digging into the stats reveals a lot. Bing has only taken significant market share in Norh America, with less than 4% everywhere else.