Common networking
Read about whatever protocol you may think of….here.
IP-telephony
Good book in PDF format for free
VoIP Bandwidht Calculator for IP telephony
One more ok Bandwidht Calculator
One of the best SIP web sites
SIP-center
SIP forum
SIP foundry
About IP telephony with SIP
The latest about IP telephony
More about VoIP
…and more
Network design
Network Magazine
IETF (Internet Engineering Task Force)
Network security
Microsoft security site
Linux based port scanner
Mobile solutions (WLAN, User mobility, etc)
Information about WLAN/WI-FI
3G links
3G-Generation
UMTS (3GPP) standardisation
CDMA2000 (3GPP2) standardisation
Project Management
PMI Project Management Institute
Prince2 Project Management Method