Internet ad spending grew by 49 percent during the first half of the year, leading all other media types, according to Nielsen//NetRatings. Overall ad spending was up 5.1 percent for the same period.

Spending on the Internet topped $3.8 billion between January and June, compared to $2.6 billion last year.

Among the verticals that increased their use of online marketing, telecommunications led the pack with a 122 percent increase in spending compared to the year-ago period. The financial services, retail goods and services and Web media sectors also reported significant growth.

"Internet spending continues to show exceptional growth as advertisers look for additional means to reach their target audiences," said Jeff King, managing director of Nielsen Monitor-Plus, in a statement.

The growth in Internet ad spending outpaced that of all other media. Coming in second was Spanish language television, which surged by 21.8 percent, likely due to World Cup broadcasts. Spot radio, local newspaper, B2B magazines, national cable TV, FSI coupon and smaller spot TV markets each showed little growth.