I would like to create a dmoz like website, using WP.
Any suggestions on plugins or site's architecture would be welcomed.
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If you want to allow visitors to submit sites, you could perhaps use the TDO Mini Forms plugin to allow visitors to create a new listing, and adjust the settings so that any new listings created through that form get held for administrator approval before being published.
A bit of extra info. In case you want to have you're site in Hebrew, TDO Mini Forms will not work. The configuration part of the plugin fails once you try to change strings to hebrew.
See this post by Nitzan Brumer for a good example on how to create a custom user-generated-content page.