What are the security concerns I need to consider while coding?

Question

I know SQL Injection is one... what are the others...

Answer 1

Never store plaintext passwords, either. (I can't tell you how many commercial packages I've evaluated for my company which did -- and then acted nonchalant about it when I called them out. My favorite excuse, from a CRM vendor: "Will your end users typically have Enterprise Manager or Query Analyzer on their desktops?")