IP Planning and Subnetting Reference Table
Subnet Planning document (a subnet planning walkthrough) (Requires Adobe Acrobat Reader)
SubnetOnline website
LearnToSubnet website
Interactive/Online Subnetting Practice webpage from San Bernardino Valley College. Nifty!
3COM website .PDF file, 40 pages, Click HERE to get to their whitepapers page, and then click on the "Understanding IP Addressing: Everything You Ever Wanted To Know" link
IP Calculator software tool
At the request of student, Chris Walter, I have posted the IETF recommended PRIVATE IP ADDRESS SCHEMES (I've copied these directly from RFC 1597)
The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private networks:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255