Get all customer groups in Magento

$customer_group = new Mage_Customer_Model_Group();

$allGroups  = $customer_group->getCollection()->toOptionHash();

foreach($allGroups as $key=>$allGroup){

   $customerGroup[$key]=array('value'=>$allGroup,'label'=>$allGroup);

}

return $customerGroup;

Get all websites and stores in Magento

foreach (Mage::app()->getWebsites() as $website) {
    foreach ($website->getGroups() as $group) {
        $stores = $group->getStores();
        foreach ($stores as $store) {
            //$store is a store object
        }
    }
}

Add Custom Field in the Billing and Shipping Address of Onepage Checkout in Magento

How to Add Custom Field in the Billing and Shipping Address of Onepage Checkout in Magento

http://indiestechtips.wordpress.com/2011/07/30/how-to-add-custom-field-in-the-billing-and-shipping-address-of-onepage-checkout-in-magento/

Magento: Admin Grid Column types

There are many types of column types in the admin grid.

Following are the list of available types in Magento:

1. date
2. datetime
3. number
4. currency
5. price
6. country
7. concat
8. action
9. options
10. checkbox
11. massaction
12. radio
13. input
14. select
15. text
16. store
17. wrapline
18. theme

Custom Events in Magento

http://stackoverflow.com/questions/1921057/custom-events-in-magento

Change Rupee Currency Symbol In Magento

Open /lib/Zend/Locale/Data/root.xml file and look for

<symbol>Rs</symbol>

Replace with

<symbol><![CDATA[New Symbol For Rupee Goes Here]]></symbol>

Override the file.

Remove the Magento cache and refresh the product page.

You are done !!!!!!!!!!!!!!!!

Implementing Google ReCaptcha Using PHP

PHP:
https://developers.google.com/recaptcha/docs/php


Magento:
http://opensourcetalking.com/magento/magento-captcha-with-recaptcha.html