Best plugin for members only access?

I have a blog where I report on legal current awareness for users who pay a monthly subscription. I just moved over from WordPress.com and I need to figure out how to make this available to subscribers only. And quickly. What I need:

– ability to easily add and remove subscribers (sometimes I provide 30 day free trials)
– enable access to the entire site via password only
– relatively easy sign up process for subscribers – they’re lawyers with no patience.

Suggestions?