Simple but powerful tool to create little diagrams on the Mac? [closed]

You want OmniGraffle. It is designed to do exactly what you want. It used to come with OS X, but hasn't since 10.3, I think.

"I use xmind for that sort of thing. .

I doubt if you'll anything really simple that does all that you want, and I agree with those who recommend Omnigraffle.

Xmind though has a much better price, free. (and it's open source if that matters)"

"This is what I use:
http://www.simplediagrams.com/

It is the least headachy for all my needs, and produces lovely output that is soft on the brain (check it out and see what I mean)."

I would recommmend Lucidchart which I have used for nearly 3 years now. It's web-based so you can use it on any operating system and it has all the features you've described (and some other nice ones).