Enhanced User Profiles with Joomla - Don't use a hammer
One of the complaints I've seen often about Joomla is that the registration process on your site doesn't gather enough data. As supplied it's restricted to asking for just the name and email address which for many people is just not enough.
As a result people have resorted to installing something like Community Builder just for the enhanced registration form without using any of the additional "social" features that Community Builder offers.
That's just using a sledgehammer to crack a nut
There is a little known plugin available for Joomla 1.5 called "usermeta" which Steve Burge has written a very good tutorial about. With this plugin you can easily add as many additional fields as you want to your registration form.
Joomla 1.6 Hidden Little Secret
With Joomla 1.6 it is even easier as everything you need is already in the core joomla installation. But it's hidden away as a disabled plugin and clearly many people haven't found it yet and are still using their sledgehammers.
User Profile Plugin
The User Profile plugin is an incredibly simple plugin that once enabled will add numerous additional fields to your web site registration form and you won't be restricted to the default name, email and password any more.
Don't want to know the new user's favourite book then just disable that field. Want to force the user to agree to your terms of service or to confirm their date of birth then just make those profile fields required.
Still need more fields
If the fields provided in the plugin are still not enough for you don't reach for that sledgehammer again!! Head on over to the Joomla documentation web site where you will find instructions for how to create additional user profile plugins which will offer even more power and possibilities to your registration forms.