What 3rd party libraries are available for iPhone development?

I'm doing iPhone programming after 10+ years as a Java developer.

In the Java world, I'm accustomed to using 3rd party libraries for just about everything, from entire frameworks like Spring to small things like the apache commons utilities.

Are there similar things available for iPhone development? Where do I find them?

I attended the WWDC conference this year but it was of no help in this matter. Apple seems to think everyone writes all their own code from scratch. That seems unlikely.

Thanks.

Two that I like out of many

http://code.google.com/p/sqlitepersistentobjects/ like orm for sqlite

And OpenCV can be used on iphone http://lambdajive.wordpress.com/2008/12/20/cross-compiling-for-iphone/

Core Plot is for both MacOS and iOS.

Three20 seems popular but I have not used it.

PhoneGap is intended as a platform but has some utility as a library.

cocos2d is a popular sprite animation library.