Micro-blogging site Twitter plans to introduce tools and services by year-end to help businesses serve their customers, and may charge fees for such services, co-founder Biz Stone said on Monday.

We're looking at who's using Twitter and for what, Stone told the Reuters Global Technology Summit in New York via videolink from San Francisco. Are there any commercial usages that are making a lot of sense?

Twitter, a two-year-old, venture capital-backed company that lets people send 140-character messages, or Tweets, has enjoyed explosive growth in recent months. Visitors to Twitter jumped 83 percent in April from the previous month, to reach 17 million, according to comScore data.

Twitter is searching for ways to make money from its popularity. Stone said phase one of that effort was spent collecting intelligence on how people use the service.

The second phase will see Twitter launching tools and services on top of free micro-blogging, aimed at companies that wish to use Twitter to message customers.

It will be simple stuff such as lightweight analytics, Stone said. He reiterated the company's commitment to keeping the service free for everyone but added:

If there is a way we can go above and beyond, and they (companies) can improve bottom line by offering services we can offer for a fee, (we) will do that.

(For summit blog: http://blogs.reuters.com/summits/)

(Reporting by Anupreeta Das and Alexei Oreskovic, editing by Tiffany Wu and John Wallace)

For Reuters MediaFile blog see http://blogs.reuters.com/mediafile/