While not absolutely necessary, I found the following resources to be extremely beneficial:
1) Safari Books Online- Any IT certification seeker will generally spend hundreds of dollars a year on books. Hell, if you pay list you’ll drop $170 on just the two volumes of Routing TCP/IP. On top of the high cost of technology books (second only to the over-inflated cost of college textbooks in my experience) is the fact that the information in a number of these books will be obsolete within a relatively short period of time. Just looking at my pile of books about NT MCSE, IIS 5, Crystal Report 8.5…confirms this. Another shortcoming of these expensive and heavy tomes is portability. Who wants to lug around several pounds of books. Especially when you’ll most likely only need a small section of that information.
Safari Books Online (I think that this is about the third different name for this service) overcomes all of these limitations. For $43 a month you get unlimited access to thousands of titles. For a more reasonable $23 a month you can access up to ten titles a month (that’s the plan that I currently use). I would suggest getting the unlimited bookshelf if you (or – better yet – your employer) can foot the cost. I only use the limited bookshelf because I have access to all of the Cisco Press books in PDF form via Cisco Advanced Services. Since that’s 95% of my tech reading, I just use Safari for the O’Reilly books and for subjects outside of networking, like like web design.
Another benefit is that you will sometimes have access to books that have not been printed yet. For instance the new CCIE Routing and Switching Practice Labs version is available on Safari. This book has not been released in physical form yet. You could purchase the Short Cuts PDF version from Cisco Press, but that will set you back abou $80. On the opposite end of the spectrum, you have access to books that are no longer in print. Need that CCNP Support Exam Certification Guide from 2000? It’s there. 
While the search feature can be crap sometimes, I do like the fact that the search will search the content of the books. You’ll need to make your searches pretty specific for best results. For instance “bgp orf” yielded 13 books and the specific chapters where that technology is discussed.
2) Cisco Live Virtual- Since I went on and on about Safari, I’ll keep this one short and sweet. For $250 you can get access to (almost?) all of the presentations and techtorials from Cisco Networkers (whatever the fuck they call it nowadays). If you attended Networkers then you’ll automatically have access to these seminars. I LOVE these. Although the ‘video’ is (at least the last few years) simply slides with audio, you can learn a ton from these seminars. It’s like being in a Networkers’ seminar without the horrible hangover.
