If you're running a company or game, or website that collects data from users and customers there's an fairly simple and safe way to store and process that information without having to write your database processing code.
I've been using SugarCRM at work for the past 2 years and its REST/SOAP API makes it a breeze to write a front-facing login for users, gather their info, and track their activities across your website (such as downloading products, or buying products). There's a great PHP API out there (https://github.com/asakusuma/SugarCRM-R ... pper-Class) that can help you write a login or user registration processor in as little as 40 lines or so.
SugarCRM has a free, open source version called Sugar Community Edition (SugarCE) which you can download from http://www.sugarcrm.com/download (the link is a bit hard to find on the main site).
Here's a few addition links:
http://www.sugaroutfitters.com (Great 3rd party module/toolkit site with professional add-ons).