Many resources are available, some in question are:
Principles to keep in mind if you want your applications to be secure:
There are some excellent books and articles online about making your applications secure:
Train your developers on application security best pratices
Security Compass (paid)
OWASP WebGoat (free)
Check out Writing Secure Code by Michael Howard and David LeBlanc from Microsoft Press. It's got a lot of good information on secure coding in general as well as a chapter or two specific to web programming. It's a Microsoft book but most of the ideas translate to whatever language you are working in.
Link to Amazon.