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)

Google (60.2% search share) and Yahoo! (17.4% search share) were the number one- and number two-ranked online search providers in the U.S. for July, according to Nielsen Online. 
AT&T Worldnet Search showed the largest year-over-year growth (+210%) for that time period. 

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

All Search
7,996,956
3%
100.0%

Google Search
4,812,974
16%
60.2%

Yahoo! Search
1,393,723
-11%
17.4%

MSN/Windows Live Search
951,882
-10%
11.9%

AOL Search
369,611
-9%
4.6%

Ask.com Search
162,337
13%
2.0%

Comcast Search
45,511
22%
0.6%

My Web Search
43,085
-38%
0.5%

AT&T Worldnet Search
33,128
210%
0.4%

NexTag Search
21,218
5%
0.3%

Dogpile.com Search
17,270
-33%
0.2%

Source: The Nielsen Company (July 1, 2008 – July 31, 2008)

Search providers are ranked by the total number of search queries conducted at the provider.
Read coverage of Nielsen’s findings on CNET, Silicon Alley Insider, and in Mediaweek.