Nielsen Online today reported data for the top U.S. search providers, ranked by total searches, the top companies/divisions and web brands in May 2009.  Total searches increased 20 percent over May 2008.
Top 10 Search Providers for May 2009 (U.S.) 

Provider
Searches (000)
YOY Growth
Share of Searches

All Search
9,440,467
20.3%
100.0%

Google Search
5,968,840
28.2%
63.2%

Yahoo! Search
1,625,253
22.3%
17.2%

MSN/Windows Live Search
891,502
-14.6%
9.4%

AOL Search
364,784
13.1%
3.9%

Ask.com Search
205,438
21.9%
2.2%

My Web Search
77,283
44.7%
0.8%

Comcast Search
55,853
33.1%
0.6%

Yellow Pages Search
33,141
n/a*
0.4%

NexTag Search
27,189
29.9%
0.3%

AT&T Worldnet Search
17,719
-32.4%
0.2%

Source: Nielsen MegaView Search

 * A year-over-year comparison is not possible because of a definitional change to Yellow Pages Search.

Google (60% search share) and Yahoo! (18.1% search share) were the number one- and number two-ranked online search providers in the U.S. for August, according to Nielsen Online.
AT&T Worldnet Search (+203.8%) and Comcast Search (+30.9%) showed the largest year-over-year growth for the time period.

Provider
Searches
(in 000’s)
Year-Over-Year
Growth
Share
of Searches

All Search Providers
7,222,826
-7.7%
100.0%

Google Search
4,331,153
3.1%
60.0%

Yahoo! Search
1,304,889
-16.5%
18.1%

MSN/Windows Live Search
770,592
-23.8%
10.7%

AOL Search
376,331
-13.5%
5.2%

Ask.com Search
143,231
4.7%
2.0%

Comcast Search
45,438
30.9%
0.6%

My Web Search
38,550
-46.3%
0.5%

AT&T Worldnet Search
30,272
203.8%
0.4%

NexTag Search
17,901
-20.6%
0.2%

Dogpile.com Search
15,418
-27.8%
0.2%

Source: The Nielsen Company (August 1, 2008 - August 31, 2008)