I typed "create" and found this gem:
It's called Create Your Own TD 2. It has about 7,000 views but it has an awesome score of 4.03. This is probably the most in-depth tower defense creator I've seen in Flash. Apart from the almost-user-friendly interface, it's perfect for those who say "oh I can make a better game than that" because it gives you all of the tools and a portal to upload your maps to. (Login for another site is required, though.) I'd say this is the best creator game I've ever played on Newgrounds.