Blender 3D: HotKeys/Key/C

C

• CKEY - (Pre-Blender-2.5) Centers the 3D View where the 3D cursor currently is.
• CKEY — (Blender 2.5) Circle Select. Use NUM+ to increase, NUM- to decrease, or MW to adjust the circle size. Drag over vertices/edges/faces with LMB to add them to selection, MMB to remove them from selection. Leave Circle Select with RMB or ESC.

• ALT+CKEY - brings up the convert menu.
• CTRL+CKEY - brings up the copy menu. This menu copies information from the active object to (other) selected objects.
• SHIFT+CKEY - CentreZero View. The 3DCursor is set to zero (0,0,0) and the view is changed so that all Objects, including the 3Dcursor, can be displayed. This is an alternative for HOME.