Hi Huy,
Here's a couple of other links that will help you out...
There are a ton of open source modules for Dnn in the forge, look through there and you usually find what you are looking for for the requirements for you site, the forge is found here.
For development of extra functionality Clint's Module Development blog series is a great start, follow this and you can't go wrong.
Another place to find great information is DnnHero, its a subscription service that gives reviews, advice and programming tips and tricks.A really good site and worth the small subscription amount for the info supplied.
The Dnn Blog is also a great resource, there are various blogs there with great information.
To save the best for last, the Dnn Community! There is always someone there to answer any questions you have about the Dnn cms. You have a choice, there is the Dnn Forums and the Community Exchange, ask there and you'll get answers to you questions.
Hope this helps,
regards,
geoff