From Project 1999 Wiki
Project 1999 is a free to play Emulated Everquest Server giving players the opportunity to experience Classic EQ once again, starting with the original 3 continents and a max level of 50,
with the look and feel of the old interface and several modifications making game mechanics similar to how the game used to be.
Project 1999 is the best and most popular classic Everquest experience.
Class Population Breakdown
Here is a nice chart posted by Uthgaard on 07-01-2011. It shows on Project 1999 the relative breakdown among active players based on class and level.