Figured we should have a thread devoted to tips, tricks, and links for modding/map making through Sandbox Editor 2.
Crymod.com is a great source of info, it has some of the Crytek developers onboard to help out, and one has even written a few very informative tutorials to get you started.
In the 2 or 3 hours I spent last night messing around, I can see Sandbox2 becoming very efficient at making solid maps. You can access a great amount of info right inside the editor itself and even has a model viewer to view character models (no clue how to use it other than look at things right now).