Adding a Member Login and PM System for Blog

Hi,

I would like to consider implementing a member login area for my blog to provide members access to a private messaging system in order to promote communication between members of my site.

Originally I thought of simply adding a forum plug-in, but after investigating that avenue it looks like it is going to be more to manage than I will probably have time for.

Is anyone using any programs which established a login area and pm system for members to your WordPress blog? If so, can you let me know what you are using, and how it has been working for you, and if there have been any security concerns adding the scripts or programs to your blog.

BTW, Just to clarify, I’m not looking for something to provide members access to my admin login area of my blog. I only want them to be able to access a member login for the purpose of accessing a private messaging system to communicate with other members.

Thank you in advance for any ideas or help you could offer!