UI Guidelines:

iPhone, iPod Touch, and iPad. Big collection of these available here which I need to parse out http://www.queness.com/post/10870/useful-collection-of-ios-tools-and-resources-for-designers

• Designing for iOS7 from developer.apple.

• iPhone Human Interface Guidelines from developer.apple.

• iPhone Human Interface Guidelines from developer.apple. (PDF)

• iPad Human Interface Guidelines from developer.apple.

• iPad Human Interface Guidelines (PDF)

• The iOS 7 Design Cheat Sheet from Ivo Mynttinen.

• iOS UI Element Guidelines which despite other tools I use several times a week... well, I used to but the iOS 7 update messed it up pretty bad.

Stencils & Templates:

• iOS7 GUI PSD (iPhone) from Teehan-Lax (Photoshop).

• iOS GUI for Sketch from Teehan-Lax (Sketch).

• IOS7 GUI Fantastic Set With More Than A Thousand Elements, from DesignShock. (Photoshop)

• iPhone 5 Grid a 10-column grid for comps. (Photoshop)

• iOS 7 Wireframe Kit in B&W, for classic wireframing. (Illustrator)

• iOS 7 WIreframe Kit for iPhone, from Funsize. (Keynote)

• Ipad Retina Mockup (Psd) from blugraphic. (Photoshop)

• Library of iOS7 UI Elements (Photoshop)

• Library of iPhone UI Elements Photoshop library of iPhone-specific elements only, from Teehan-Lax. Updated occasionally, so if you see a new one, please update the link for us. (Photoshop)

• http://www.teehanlax.com/blog/2010/08/12/iphone-4-gui-psd-retina-display/ Same as above but for the iPhone 4 resolution instead. (Photoshop)

• iPhone UI Kit Lots of UI widgets like switches, buttons, etc. (Photoshop)

• Another Libtary of iPhone4 UI Elements Based on the Teehan-Lax work above, but presumably different in some way. (Photoshop)

• Vector Wireframe Templates for iPhone (Illustrator)

• iPhone 4 HD Another one, not sure who made it or if it's fresh or a derivation of the Teehan-Lax stuff again. (Photoshop)

• iPhone Wireframe Kit In, of all things, Google Docs. Haven't tried it, but I really need to. (GoogleDocs)

• iPad Template Preview only has the frame, so not sure what is included. (Photoshop)

• iPad Wall Presenter I think just the frames with guides to put backgrounds and designs into. (PNG and Photoshop)

• Sketching the iPad from Zurb to encourage sketching, even as far as to print empties and use your mad Sharpie® skills. (OmniGraffle)

• iPad and iPhone Design by da5id, via Graffletopia. (OmniGraffle)

• iOS Application Icon Template from The Icon Handbook. (Illustrator)

• iPhone & iPad PSD templates & icons by Rafi (Photoshop)

• MOObileFrames iOS Wireframe Tool from Raiz Labs. (Keynote, Powerpoint)

• iPad Template for Visio from IconSlinger. (Visio of course)

• UI Pack for iOS from rebirthPIXEL. Lots of faux-leather and other skeuomorphic textures. (Photoshop)