CDMA technology explain
Janus Krarup MOT GSM programming info page
GSM info World Wide (Networks , Roaming , System)
Cellular Telephone Basics
Forum for lot of cellular info (Include iDEN)
Cellular & PCS site guide
RadioPhone Cellular info
A huge Cellular Info Site (include iDEN)
DDI Software for Windows/Linux and Sound card

Wireless Aplication Protocol (WAP) info

This Place allow you to Send E-mail from Your GSM phone via SMS Message