The topics that you mentioned are actually a sample of three different certification paths. To start, Cisco has a Wireless Specialist certification that specializes in the Cisco Aironet products in a wireless LAN infrastructure. However, it is important to note that these certifications require you to pass the CCDA exam to become a Wireless Specialist.
As for VPN, you can take the brand new 642-551 Securing Cisco Network Devices (SND) exam along with the 642-511 Cisco Secure Virtual Private Networks (CSVPN) exam and become a Cisco VPN Specialist. At that point, you are three exams away from becoming a CCSP if you wish to pursue the rest of the security track.
Similarly, the 642-432 Cisco Voice over IP (CVOICE) exam contains topics revolving around the implementation and configuration of the Cisco VoIP routers. That exam coupled with four other exams will earn you the CCVP certification.
With so many paths ahead of you, pick which technology interests you the most and run with it. Once you have exhausted that track, hop on to another one and go from there.
This was first published in October 2005