Cool iPhone Overlay UI

http://developer.apple.com/iPhone/library/samplecode/HeadsUpUI/index.html

also:

http://www.skylarcantu.com/blog/2009/08/14/custom-uialertview-color-chooser/

Screen grab:

http://www.skylarcantu.com/blog/2009/10/16/saving-a-view-as-an-image/#more-299

In general a good read:

http://www.skylarcantu.com/blog/category/iphone-development/

http://joris.kluivers.nl/iphone-dev/?p=CustomAlert