A Quick Start Guide - Getting Your Avatar Through New Media Consortium (NMC)

A Quick Start Guide - Getting Your Avatar Through Linden Labs

Things You Must Know Before You Go Exploring

SL Glossary

Helpful Appearance Settings Starting Points

Navigation Controls Cheat Sheet - Covers flying, how to see yourself, etc.

How Do I - Some Common Questions Answered

What To Do About Griefers

What Can Be Done To Lessen Lag

Other SL Tips From The Web

A Printeable PDF Keyboard Cheatsheet (thanks for passing along Erin!)
http://www.kippiefriedkin.com/resources/secondlife-viewer-cheatsheet.pdf