Here is a collection of links that you may or may not find useful, but they are here more so that I don't lose them.
- Regular Expression Test Tool
Using this tool you can test both ereg and preg functions. Enter your regular expression syntax and your data and this tool will return what the actual function returns so that you can test your regular expressions without having to upload new files to your server each time.
- MySQL Field Types
This chart lists out every MySQL field type you could ever think of using. It helps you choose the right type of field, for example, whether to use SMALLINT or MEDIUMINT, this chart gives you the range of values that are accepted.