From how I see it - in Worlds 1 to 3 as well as any clan war worlds or other trading worlds, during the day, are almost always full or near full (depending on who is coming in and out of the world at the time). Putting those aside, on average, you see about 300 people per server.
As of 9 November, 2009, there are 169 Runescape worlds. 88 for free players, 81 for Members.
No, but there are different servers and more mini servers in game.
There are 159 worlds including the 4 dutch worlds
Currently, it's 82 member worlds in all of RuneScape, whereas 5 is in other languages.
yes.
on the pvp/bounty worlds
about 35
as in worlds? then yes, 58.22.101.138
Whenever you log out to the lobby, you are placed in one of several "lobby worlds". There seem to be several servers for the lobby; one is chosen for you automatically. You can't control which one, nor would it benefit you if you could.
runescape
In the Edgeville bank, on BH worlds.
Take a look on the world selection.