Network for Good and Groundspring, two of the largest nonprofit groups offering Internet-based fundraising and donor-management services to nonprofits, are merging.

The combined organization, to be called Network for Good, will continue to offer and service both groups' original donation tools and services, and plan to integrate and expand their products for nonprofits.

Bill Strathmann, CEO of Network for Good, will retain his title within the new company, and Joseph Mouzon, executive director and chief operating officer of Groundspring, will become executive director of nonprofit services for the combined entity.

Three representatives of the Tides Foundation, which founded Groundspring in 1999, will join the board of Network for Good.

Network for Good, headquartered in Bethesda, Md., let donors contribute to more than 1 million nonprofits through its website, which has raised a total of $70 million since its founding in 2001, the company says.

It also offers web-based services allowing its 4,000 nonprofit clients to receive donations on their own websites.

Groundspring, located in San Francisco, offers training and donation services that have raised more than $15.4 million for nonprofits since its inception, the company says.

The groups are planning to sign a definitive merger agreement by the end of the week.