Probably the two most obvious and largest known quest repositories are:
But they're not the only places to get quests! If you guys have any quest demoes or web pages you've made for your quests, feel free to post them here. The more the merrier!
For your reference, the old thread is http://armageddongames.net/showthread.php?55879-Quest-links(please-look-here-before-requesting-quests)-1-0