If you are responsible for the web server or web application security, go read Microsoft Security Advisory 954462, Rise in SQL Injection Attacks Exploiting Unverified User Data Input immediately. It contains important information on detecting and mitigating SQL injection vulnerabilities.
This advisory is not specific to only Microsoft products like the IIS web server and SQL database. Other web servers and database programs are also vulnerable to these attacks.
You may also want to check out the Top 15 free SQL Injection Scanners and check your own web sites for vulnerabilities.