A series that teaches you singing techniques and exercises

http://jameslugo.com/order.shtml

I've always searched for a good info on singing techniques. Here's one I found from James Lugo. It's well priced and looks the part. I'll be recommending this to my singers.

Check broken links on websites

http://validator.w3.org/checklink

The above site is a free service that allows webmasters to check for broken links on their site.