Everything you ever wanted to know about TCP/IP. 3COM TCP/IP Whitepaper.  This is a very thorough and easy to understand paper on subnetting.  I used this paper instead of Microsoft's documentation since I found Microsoft's confusing and at times, incorrect.

An exhaustive List of TCP/IP ports. Helpful for determining what ports are used for which services so you can configure the "Advanced" TCP/IP properties of NT and make your system more secure.  Ports

Be sure you understand the name resolution orders before taking your exam.  The majority of the exam is comprised of troubleshooting name resolution problems.  For example, a question might ask present a scenario where you can connect to a UNIX server, but not a Microsoft server.  What should you check for to make sure name resolution is working properly?  For a helpful summary chart check out  Netbios Name Resolution.

Excellent site regarding encryption. A little on the technical side but excellent for Public/Private Key Encryption.

Internet Utilities including an Web based trace route and nslookup in case you are behind a firewall.  HIS/

Need to know more about newsgroup moderation?

ODBC Errors for IIS 4.0 exam!

If you are having trouble with Microsoft's DNS, read their whitepaper on DNS.  It is about 30 pages, fairly thorough and easy to understand.  If you understand the whitepaper, you won't be caught off guard on the exam or in the real world. To understand NT 4.0 DNS read MSDN DNS Whitepaper but if your working on Windows 2000 DNS and Active Directory you should read Windows 2000 DNS

Subnet Tables
    Class A Table
    Class B Table
    Class C Table