I see roughly two types of worlds where I look, being "base game compatible" of with (a lot of) CC. Are there also worlds that use the contents and have the rabbit holes/lots from all packs, but do not use any cc or premium content? I.e. if you have just all of the 20 packs installed and nothing else, you would have the perfect town ready to go play in?
I don't think this blog is active anymore, but it's still up and I know has a at least 1 or maybe even 2 worlds that are cc free: http://sims3customworlds.tumblr.com/
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http://sims3customworlds.tumblr.com/
And over at MATY, Anach has a download link available for Expanded Sunset Valley made with 0 CC and 0 Store content (scroll down in the thread a bit to find the link):
http://www.moreawesomethanyou.com/smf/index.php/topic,17647.0.html
The official Sims 3 Exchange also has quite a few worlds that are CC free, believe it or not.
The Winters family Tree --- My Mods
*Edit: Quailhogs has created some incredible worlds that don't use CC. They have also created some interesting characters for those worlds.
And rflong7 is a prolific and creative world builder that has many different types of worlds ready to go.