The web has an enormous array of resources about GIS and mapping. Here's a select set:

Oddens Fascinating World of Maps  - the most incredible collection of mapping and GIS links in the world

Geography Network - a general clearinghouse about GIS and online GIS data

ESRI Mapping Center - a blog and gallery and more about making maps (ArcGIS focused)

NCGIA – National Center for Geographic Information  - the federal base for information about GIS and related technology

Directions Magazine  - an online magazine about the business of GIS, very good and current trends and reviews

AllPoints Blog - a blog about GIS and location technology, published by Directions magazine

Planet Geospatial - a daily blog about GIS and related technology

SlashGeo - a daily blog about GIS and related technology

Google Earth Blog and Google Earth Outreach - updates on Google Earth and lots of resources for non-profit use of Google Earth.