Americans gave $23.5 billion to charities last year, giving most generously to the Salvation Army, the American Red Cross and Catholic Charities USA.

Giving was up 5 percent from a year earlier, The Chronicle of Philanthropy's annual survey of the 400 nonprofit organizations receiving the most private money showed. The 1994 increase was 6.3 percent.The list includes about $1 out of every $6 donated to nonprofits.

Although donations to the Salvation Army dropped by 11.3 percent, that organization topped the list for the fourth consecutive year with collections of $644.3 million.

The American Red Cross, number two for three years, raised $456.6 million, which represented a 7.9 percent drop from 1994.

A 25-percent increase in giving to Catholic Charities USA boosted that organization from No. 7 to No. 3 on the list, as it raised $419.4 million last year.

Overall, human-service groups found giving down 5.3 percent.

The survey also found:

-Community foundations, which raise and distribute money in a single geographic area, saw the biggest gain in donations - 93 percent.

-Giving rose 25.4 percent to museums and libraries, 17.5 percent to education groups, 17.4 percent to public broadcasting and 16.5 percent to arts organizations.

-Public affairs groups saw giving drop sharpest, by 8.2 percent.

-The 400 top charities include 138 colleges and universities, 45 United Way organizations, 34 international groups, 21 human-service groups, 24 religious organi-zations, 21 health charities and 21 hospital and medical centers.

Rounding out the top 10 charities, in order, were the American Cancer Society; Second Harvest, a national network of food banks; the United Jewish Appeal; Harvard University; Boys and Girls Clubs of America; the YWCA of the USA; and the American Heart Association.