Every skill goes to 99, and every level adds to your total. New content opens at levels 1, 20, 40, 60, 80.
Melee
Ranged
Magic
Hitpoints
Prayer
Fishing
Mining
Woodcutting
Farming
Sailing
Cooking
Smithing
Crafting
Brewing
Fletching
Essence Binding
Agility
Bounty