I'm going to use this thread to maintain a list of texture, music and other royalty-free resources, so that DB programmers have a head start, instead of having to google around the interwebs
royalty-free textures
http://www.cgtextures.com
An amazing collection. Thousands of textures in hundreds of catagories. The free account is very worthwhile, but I can also recommend a paid membership. The paid membership textures are huge and of a very high standard, lots are tileable and some have normal maps included. The help section explains how to create normal maps from any texture.
royalty-free music
http://www.audionautix.com
http://www.incompetech.com/m/c/royalty-free
Amazing collection of free music. I spent hours just browsing them