All three of the areas about which you inquire -- namely, VoIP, network/information security, and SAN -- present excellent employment opportunities for knowledgeable, experienced practitioners where VoIP and SAN probably present the best opportunities for entry-level professionals as well. When it comes to VoIP, start with a vendor-neutral cert like the CTP or CCNT (see my survey of VoIP certs for more information), and then move into whichever vendor platform you feel offers the best mix of on-the-job experience and learning opportunities (Cisco and Avaya are both good choices). When it comes to SAN/NAS, start with SNIA (Storage Networking Industry Association) credentials and then, likewise, jump into the vendor platform of choice (I wrote an article on storage-related programs and certifications for Certmag in 2003, but it's a bit out of date now).
Thanks for posting. Good luck with your career planning and training activities!
This was first published in April 2007