The top 5 Feed the Beast Unleashed seeds (In my opinion). Enjoy.
#1 - Plenty O'Biomes! (Request)
Unleashed V1.1.1
Biomes O'Plenty World Generation
Seed: 1955281591006031943
#2 - Plenty O'Biomes: The Sequel!
Unleashed v1.1.3
Biomes O'Plenty World Generation
Seed: 1772835215
#3 - Most Amazing Mountains Ever!
Unleashed V1.1.3
Biomes O'Plenty World Generation
Seed: 2323115871908605002
#4 - Spawn Mountains & Floating Islands!
Unleashed V1.1.3
Biomes O'Plenty World Generation
Seed: -16204873
#5 - Triple Ravine / Mineshaft / Diamonds / End Portal / Dungeons
Unleashed v1.0.3
Biomes O'Plenty World Generation
Seed: -9057352651117540831