aMember is basically a backend subscription management system. It provides you with a signup, login, and management system, that you then integrate with other softwares such as CMS (content management system), BBS, help desks etc.

Built in 1-tier affiliate system.

It is recommended for intermediate users, as it does require some HTML knowledge, and limited PHP knowledge is also recommended. 

Membergate is a high end solution for large membership sites. It is a turnkey system that has a built in CMS, forums etc.

Built in 1-tier affiliate system.

It is recommended for beginner to advanced users who want a turnkey solution and are planning on having a large user base. 

Visiongate provides a hosted solution. They provide up to 6gb of space and 50gb of transfer monthly.  Visiongate has many of the integrations you will need for your membership site.  Since it is a hosted solution, you may not be able to make custominzations to the code, or integrate it with 3rd party scripts.

 No built in affiliate program. However a 3rd party affiliate program maybe possible.

JV Manager claims to be a complete business manager. It handles digital product sales, affiliate programs and managing membership sites on multiple domains. Many marketers swear by it. However, there are many resllers selling it, so its difficult to know the hype from actual value of the product. 

If you are using this product and not a resller, please post your review! 

Memberstar is a hosted solution. They offer a WYSIWYG editor to edit pages. Also included are forums, polls and autoresponders.

It has a built in affiliate program 

You will not be able to do anything that requires customization of the code.

It is recommended for beginner to advanced users and it may be a good solution if your requirements meet their abilities.

EasyMemberPro is an self install solution, with a CMS system built in.

They offer 2 plan2, a 1 site license and unlimited. It's unclear if this means you can use it on multiple sites, but according to the website, in order to offer multiple membership levels on the same site, you need the unlimited version.

This may be a solution if you only have 1 type of membership to sell and do no want to do any html coding.

Launch Formula Marketing is a basic membership system seeming to focus on the sales of set products and content. It Allows the timed release of content depending on a members sign up date. 

The affiliate program is 1 tier, and allows you to set different payments to different groups.

Strongpoints: Easy to install, clean interface. It seems to be good at member management, and provides a simple payment system.

Weakpoints: Poor at content management, and no ability to integrate CMS, Forums etc.

It is recommended for beginner to advanced, you should know some basic HTML to create the header, footer and content. 

Installation Videos can be seen here:

http://launchformulamarketing.com/vids/ 

Goldbar one is an all in one payment system, autoresponder,  helpdesk, CMS, and membership system. It installs places membership systems on mulitple websites and you control them from one central interface. This allows you to build one working prototype, and then clone the system for many different sites.

They do allow the sequencing of content depending on when a new member signs up. They also have an add on which allows you to send information to a fulfillment company.

This is in their terms of service "Goldbar.net reserves the right to change fees at any time, for any reason at its sole discretion. " - a bit scary...

They also sell a video called "Membership Superstars" which I found to be more of a long sales letter than a how to on membership sites. Useful if you are interested in their software as it explains how it can be used.