BuddyPress.org

just open wp-content/themes/buddypress-home/css/base.css in a text editor and change:

#header h1 a {

text-indent: -999em;

background: url(../images/logo.gif) top left no-repeat;

overflow: hidden;

width: 214px;

height: 35px;

display: block;

float: left;

}

or simply replace wp-content/themes/buddypress-home/images/logo.gif with your logo.