There’s good news for U.S. charitable organizations: Fundraising grew for the 10th consecutive month, according to Blackbaud Inc.’s latest quarterly report released Monday.

Better yet, overall charitable revenue grew by 11.3% for the three months ended May 2011 over the previous year, the first time in a long while growth has exceeded 10%, Chuck Longfield, the firm’s chief scientist and creator of The Blackbaud Index, said in a statement. The trend is based on $2.3 billion in 12 months’ revenue from 1,383 nonprofit organizations.

Longfield noted that organizations of all sizes are experiencing growth for the first time since the onset of the recent recession. Fundraising at medium and large organizations grew by 10%, while small organizations (those with less than $1 million in annual fundraising revenue) grew by 17.6%.

 Online revenue increased by 6.7% for the three months ended May 2011, according to statement. This trend is based on $427 million in 12 months’ online revenue from 1,833 organizations.

Blackbaud also announced the rollout of a specialty index, focused on the international affairs sub-sector, which will be updated monthly. The new index was up 13% for the three-month period, reflecting significant post-Haiti growth, while fundraising at arts and culture organizations grew nearly 12%.

The increase wasn’t universal, however. Human services and environmental groups were still down from their year-earlier results. “With job growth flat the past two months and the economy weakening, a real challenge for all nonprofits going forward will be maintaining this momentum,” Longfield said.