SharePoint 2010 has introduced a new type of List called the External List. The External List is used for displaying content that comes from Business Connectivity Services (BCS) Enterprise content types. Business Connectivity Services is the replacement in SharePoint 2010 for The Business Data Catalog (BDC) in SharePoint 2007.

Sometimes with SharePoint you will find yourself in a Chicken and Egg situation! Many SharePoint specialists consider it a best practice to use many site collections in there environments than to have one big site collection. Each site collection can be assigned its own content database and therefore makes backup and restoration of SharePoint data more efficient than try to back up one huge database. This can however cause you other problems such as isolated content types, and difficulty to roll up data from lists and libraries that are distributed through multiple site collections.

Have you explored what can be done with the Business Data Catalog (BDC) yet? The BDC is no longer brand new, but is still very misunderstood and extremely powerful. Many consider it to be yet another way of displaying data in web parts, well yes, but as well as that you can search your Line of Business data (LOB), use it within SharePoint lists and Libraries from a special type of lookup column, aggregate user profile information from LOB systems into SharePoint and create your own custom applications using an extensive object model.