What are the different types of membership sites available:
There a few different types of membership websites and the good thing is you can actually make profit from each and every single one of them.
# Blog
There is the blog model, this is where you basically write blog posts on a regular basis and charge monthly for it, you can post content, how-to tutorials, guides even post images, videos, interviews with people in the niche. When using the blog model on your membership site you can also use make money from affiliate programs and PPC advertising too, you can integrate PPC ads and affiliate program links into your blog content.
# Forum
A Forum membership where you charge your users for unique access to a member only forum, this can be done in many ways, for example;
# A forum that is 100% free to join with a premium area for exclusive content to be released in these areas.
# A forum is 100% free to join with no premium areas but costs to visit links on the website, this works great for websites that share content such as ebooks, videos, files such as software, games etc.. This would show all the content and publish it so it could be found in search engines but the users would have to purchase the membership subscription to access the file. 
# A forum which costs monthly to join and there is different packages per different users, for example different levels, gold, silver and bronze, gold being able to post in all areas, post links, images, files, pm and email users, silver having restricted use and bronze having basic use.
# Newsletter
The newsletter model is where you charge to send out a daily, weekly, monthly newsletter about a certain subject, you can actually do this for free using letter.ly or you can use other more commercial ways of setting up a newsletter membership website.
# Hybrid 
A hybrid membership website is where you use more than 1 membership model at once, for example mixing a forum, blog and a newsletter together, giving you the ability to charge 3 times as much but this will require a lot more work.