I got sidetracked today on some Active Directory stuff and came across this great article by Klaus Salchner entitled LDAP, IIS and WinNT Directory Services. It also talks a fair bit about ADAM - Active Directory Application Mode.
Well worth a read.
Tristan also just found me a great MSDN article on enumerating the members of a group using System.DirectoryServices. Much nicer than the one I found that uses VBScript.