There are many Website Builder Platforms. It's an entire industry that seems to be thriving - the top 5 players having all raised millions in funding this year (2014).

This list is in no particular order. Some of them offer the ability to create membership type websites (but not in the standard way where your members would access a CMS - that can only be done custom).

Website Builder Platforms

BaseKit Based Platform (HostGator, SiteJam, etc) - http://www.basekit.com/
GoDaddy Website Builder - https://www.godaddy.com/
Jimdo - http://www.jimdo.com/
Populr - https://www.populr.me/
Readymag - https://readymag.com/
SquareSpace - http://www.squarespace.com/
Voog - http://voog.com/ (edicy back in the day)
Webflow - https://webflow.com/
Webnode - http://www.webnode.com/
Weebly - http://www.weebly.com/
Wix - http://www.wix.com/
Yola - https://www.yola.com/
Zoho Sites - https://www.zoho.com/sites/
Moonfruit - http://moonfruit.com/
Biznessweb - http://biznessweb.com/
Aircus - http://www.aircus.com/
imcreator - http://www.imcreator.com/
Cloudcannon - http://cloudcannon.com
Webydo - http://webydo.com
Sidengo - https://sidengo.com/
Homestead - http://www.homestead.com/
Virb - http://virb.com/
Breezi - http://breezi.com/
Strikingly - http://www.strikingly.com/
uCoz - http://www.ucoz.com/
Flazio - http://www.flazio.com/
Jigsy - http://jigsy.com/
Webstarts - http://www.webstarts.com/
Webs - http://www.webs.com/
Vistaprint - http://vistaprint.com/
Simplesite - http://www.simplesite.com/
SnapPages - http://snappages.com/
Exai - http://www.exai.com/
Site Sumo - http://sitesumo.com/
DoddleKit - http://www.doodlekit.com/
Pikock - http://www.pikock.com/
Gutensite - http://www.gutensite.com/
Flavors Me - http://flavors.me/
Airsquare - http://www.airsquare.com/
Mobsyte - http://www.mobsyte.com/
Pagekit - http://www.pagekit.com/
Goodsie - http://goodsie.com/
Freshcreator - http://www.freshcreator.com/
Oxxy - https://www.oxxy.com/
Cubender - http://www.cubender.com/
Lifeyo - http://www.lifeyo.com/
Froont - http://froont.com/
Mozello - http://www.mozello.com/
Pixelhub - http://pixelhub.me/
Dudamobile - http://www.dudamobile.com/
Unbounce - http://unbounce.com/
Nubook - http://nubook.com/
Zyro - http://zyro.com/
Justaddcontent - http://justaddcontent.com/
Mpress - http://mpress.me/
Livecontrol - https://www.livecontrol.net/
Rocketspark - http://www.rocketspark.com/
The Grid - https://thegrid.io/
Website - http://www.website.com/
Sitezulu - http://www.sitezulu.com/
Sitedity - http://www.sitedity.com/
Nikktto - https://nikktto.com
Website builder - http://www.website-builder.com/
Mrsite - http://mrsite.com/
Websitebuild - http://www.websitebuild.net/
Landerapp - http://landerapp.com/
Simplybuilt - https://www.simplybuilt.com
Instapage - http://www.instapage.com/
Broadsheet - http://broadsheet.io/

I'm sure there's more website builder platforms out there that are not in my list.