Athena was recently completed by Royal Huisman in the Netherlands for Jim Clark, Internet pioneer and founder of SGI, Netscape, Healtheon, etc. Athena is a 3 masted schooner of enormous proportions. Length overall (LOA) is 289 feet (90m), width (beam) is 36 feet (12m), and weighs in at over 1000 tonnes. His previous boat, Hyperion was also large, but not as large.
While Athena is currently the largest sailing ship in the world, it won't be for long. There are other, larger boats currently in construction as these rich guy try to outdo each other.
One problem is that the masts are getting so tall that they do not fit under the Bridge of the Americas which hooks up the two sides of the Panama Canal. The bridge has a clearance of 201 feet at high tide. One guy made a yacht that can only fit under the bridge at low tide, so now other rich guys are having yachts designed with telescoping masts and other clever mast-shortening devices so that they can lower while going under this bridge.
Subscribe to the British magazine "Yachting World", as they have a wonderful "Supersail" section in each issue that details various huge and amazing yachts.