Minecraft Viper Squad are a clan who run several different games and servers and own the website http://thevipersquad.weebly.com/
The clan is made up of eight current members with CommandoAir and Lola3441 being the primary owners. The whole squad list can be found on the website here, with information about how to join the clan also available: http://thevipersquad.weebly.com/members1.html
Viper Squad also feature a number of downloads on their website including Minecraft specific content, such as a downloadable launcher, which supposedly allows players who are running cracked versions of Minecraft to update illegitimately.
Minecraft clans are very easy to form and you can find more of the information you are looking for on the minecraft forum, which discusses clans and how join up. You will also find a large number of Minecraft users recruiting for clan members there too: www.minecraftforum.net/forums/servers/clans