In 1956, NBC started using a logo for their color programming. The original peacock is a lucky find today. In 1962, they changed the logo. On a kaleidoscopic background, a majestic tune plays, as the NBC peacock fans its feathers and then turns into the logo from before.
The chimes were rendered obsolete by 1960 as a new logo, dubbed the "NBC snake", arrived. There are some variants of it but the most famous is the one where it draws itself.
This short-lived abstract N logo made its debut on New Years Day 1976.
This is shown with or without the stylized "N"; although the version without the "N" was rarely seen after 1980. The network had, by this time, decided to take a new approach in its programming to introduce the slogan, "NBC--Proud As A Peacock!"
In 2011, NBC altered and modified their logo slightly to feature bevels and gradients. Other aspects of the 2009 graphics package remained intact. Currently in tandem with the 2013 CGI variant in promos, the 2011 variant is still in use until the end of the 2012-2013 television season.
In 2013, NBC altered and modified their computer-generated logo, which is currently in tandem with its 2011 counterpart that is still in use for the remainder of the 2012-13 television season.
To see more stuff from NBC go here: NBC/Others.