Buy the O'Reilly book Designing Mobile Interfaces.
584 pages of patterns, principles, tips, and tricks.
Read the wiki here.
A simple, plastic stencil to help keep the touch guidelines in mind.
Check for touch target sizes, margins, type sizes and more.
Buy one now.
CheapFREE, effective, and mobile-friendly, self-paced video training.
Lessons, exercises and references on mobile, touch, and accessibility.
The definitive research-based guidelines on design for touchscreens.
Articles, slides, videos, and hundreds of references.