If you install Domino Designer, and open the built-in help, there's a pretty good introduction to how development is done.

This wiki contains lots of good information for beginners. You might just read the whole FAQs Category; you will almost certainly run in to all these issues at some point.

Domino Designer 6 A Developer's Handbook, though a little dated, still covers the basics. Ignore the sections on web development, since this is better done using XPages now.

Every developer should read Performance basics for developers (whitepaper) to avoid creating applications which get unacceptably slow as more documents are added.

Pre built Applications

Find some good Notes templates for newbies at lotusguru.com. Picking apart others' designs is a great way to learn!

An excellent resource for developers of all experience levels, are the many free templates and code snippets at www.openntf.org.