Conquer Online has a training ground, you must stay logged in though.
The XP you gain is way slower then what you get when you grind but its still a good amount of XP gained for doing nothing. As you gain more levels you changed from pole to pole for your level, it gets slower and slower but thats just normal. You can go into training grounds when you reach level 20, doesn't take that long if you find someone to plvl you to 20 real quick.
If you can't find anyone to plvl you, just PM me, I'll gladly do it!
www.conqueronline.com
Only crappy part about the game is the company is extremely greedy.
Ask any veterans of the game and you'll see, they'll say the same thing...
Anyways, theres also WoW like everyone mentioned but its P2P, if you don't mind paying, WoW is a great game, its worth it.