Here is a compilation of the best seeds I've heard of:

SEED-blank PROPERTIES-A land that is mostly ice with some water and land in the corners. It is almost absolutely flat.

SEED-bubblegum PROPERTIES-Some islands surrounded by water and covered in trees.

SEED-helms deep PROPERTIES-Caverns, hills, cliffs and spectacular mountains.

SEED-supercalifragilistcexpialidocious PROPERTIES-Trust me, I know it's spelled wrong, but spell it exactly as I do, because there will be epic mountains, forests and much more.

SEED-mooshroom PROPERTIES-Spawns near sandstone village in the plains.

SEED-404 PROPERTIES-Desert with gravel patch... with other surprises.

SEED-flatlands PROPERTIES-Relatively flat place.

SEED-warhammer 40000 PROPERTIES-A content place.