I hold a CCNA & CCNP.
The CCNA is pretty easy, a good portion of the test centers on the OSI model and the functions of the 7 layers (like, "Layer 2 is responsible for _______" (multiple choice)), configuration operations, address Classes (A,B,C,D,E) IP addressing and subnet masking. Also, there may be some design questions like, "A campus network would be considered a _______" (multiple choice).
There may be some ACL (Access Control List) references, but I think that the most you would need to know would be IP standard (1-99) and IP extended (100-199) ACLs, which make up the vast majority of firewall configuring you'd do. Those are pretty easy and follow a simple format;
Router(config)# access-list <1-99> <permit/deny> (source.address) (source.mask)
Router(config)# access-list <100-199> <permit/deny> <udp/tcp> (source.address) (source.mask) (destination.address) (desitination.mask) eq <port.number (1-65535)>
Just remember that the source/destination mask is the inverse, so that if you want to block all but the 4th octet (/24), then you use 0.0.0.255 instead of the intuitive 255.255.255.0 that you use when addressing.
I don't remember any questions regarding DEC, AppleTalk, ISDN or such things as telephony. Mostly basics, IP & ethernet-centric.
I would recommend Introduction to Cisco Router Configuration as the only book you really need. You could also do some reading at cisco.com, they have a lot of documentation, although I don't find it well organized (lots of redundancy and hard to find specifics).
I always had access to all types of routers and switches from work, so I don't know what to recommend to those without access to such resources, but you might do some googling for Cisco IOS configs to get an idea of how standard systems are setup and configured. There are emulators and sims that you could use, but I haven't used any to make any recommendations.
Post Script: Regarding the CCNP; there is no way in hell (IMHO) that you can successfully pass the CCNP without a set of routers and manageable switches with hosts to work with. For me, it was most beneficial that I had to use them everyday for work on a MAN, so I didn't have a choice but to learn/know how to do stuff. It basically needs to become second nature to you to do just about anything you'd see in a large network with a lot of customers making various requests for services.