Are approach and departure procedures based on visual reference points official VFR procedures?
Yes, they are official, this is the KSEA MALL VISUAL RWY 34R/C/L approach plate:



I can't find a "East Channel Departure" but if you know what airport it belongs to, you can find it in the Terminal Procedures publication, either in paper form or online.

They are not VFR procedures, but rather visual IFR procedures. The MALL VISUAL would not be assigned to a VFR flight. Some airports do have special arrival/departure procedures which apply to VFR flights; these can be found in the Airport/Facilities Directory (A/FD) or on a website like http://www.airnav.com/ (for the US anyway).