On Windows Server 2008 ADAM (Active Directory Application Mode) has been changed to AD LDS (Active Directory Lightweight Directory Services). Personally I like the name ADAM better than AD LDS, I guess it just rolls off the tongue a little easier. Installing AD LDS on Windows 2008 is a bit different than installing ADAM on Windows 2003 because you no longer go to Add / Remove Programs and then Windows Features.
To install AD LDS go to Server Manager > Roles > Add A Role > Active Directory Lightweight Directory Services > and follow the instructions. To remove AD LDS you can use Add / Remove Programs just like with ADAM. Once AD LDS is installed it will appear under the Administrative Tools folder as Active Directory Lightweight Directory Services Setup Wizard, ADSI Edit (formerly ADAM ADSI edit) and Active Directory Sites and Services instead of in its own ADAM program folder.
To create a new instance click on Active Directory Lightweight Directory Services Setup Wizard in All Programs > Administrative Tools and follow the on screen wizard. These screens look similar to the screens found in ADAM so the setup process should be exactly the same.
The Connection Settings window in ADSI Edit was a little bit different than in ADAM but serves the same purpose. One difference I noticed was when I set up a connection I had to specify the computer as localhost under "Select or type a domain or server" whereas this was setup by default in ADAM.
It's good to see not everything changed, the C:\Windows\ADAM folder still exists in Windows 2008. If you need to import a database schema you'll notice there is no ADAM Tools Command Prompt link, instead open a regular command prompt window and change to the C:\Windows\ADAM directory to do your import.
Anyone who is comfortable with setting up an ADAM connection in Windows Server 2003 should be able to setup AD LDS in Windows Server 2008.