- GIS Tips and Tricks: http://www.aubreyrhea.net/gis/ - This one is no longer updated and is for 9.X, but it is still very useful.
- F yeah GIS: http://fyeahgis.tumblr.com/
- CartoTalk: http://www.cartotalk.com/ - This is a forum for cartographers. There is a thread where you can upload your map and get critiques.
- GIS Wiki: http://wiki.gis.com/wiki/index.php/Main_Page
- GIS Wiki GIS blogs: http://wiki.gis.com/wiki/index.php/List_of_GIS-related_Blogs - A list of more GIS blogs.
- A Cartographer's Toolkit: http://www.gretchenpeterson.com/blog/
Let me know if you know of any other great GIS blogs!