Our site is a Joomla 1.5 with Jomocial. I have Acajoom for our newsltetters currently but I want to transition to Constant Contact only. When people register on our site to become a User, they are currently automatically added to our Acajoom newsletter subsciber list. I would like to have this capability with Constant Contact as well. What do I need to do to integrate my site's registration module with constant contact?
If you are looking to integrate your sign up form to automatically add subscribers into your Constant Contact account, I would recommend taking a look at the Nice Constant Contact newsletter Sign-up Module. This is a plug-in for Joomla written by a third party developer, and is intended to allows visitors to your Joomla site to sign up for your Constant Contact mailing list.
If you are looking to customize this sign up form a bit more than this plug-in allows, you could always develop your own integration. Our API Doc page has a number of How-to guides on our API Functionality. In addition to this, I would recommend visiting our Sample Code page for sign up form samples that can help get you started.