There are great benefits to closely monitoring your Active Directory domain controllers. Here are some lists of daily, weekly, and monthly tasks.

Microsoft TechNet:

Scribd:

Network Steve Forum:

Looking at the suggestion in the Network Steve post one suggestion is using several CLI tools to create a report.

dcdiag /v /c /d /e /s:dcname >c:\dcdiag.txt
netdiag /v >c:\netdiag.txt
repadmin /showrepl * /verbose /all /intersite >c:\repl.tx
dnslint /ad /s "DCipaddress"
Download DNSLINT: http://support.microsoft.com/kb/321045

Expect to see some errors using DCDIAG in certain situations: DCDIAG.EXE /E or /A or /C expected errors (MS Support)

What does DCDIAG actually… do? (Ask the AD Guys Blog)

You will notice that REPLMON is no longer available in Windows Server 2008 R2.

blog.powershell.no:

Ask the Directory Services Team Blog:

NETDIAG is also no longer supported, but DCDIAG should give you all the information and ability that you need.