Online CRM's to manage Leads. Are they worth it?

Does anyone use any of the Real Estate CRM’s out there to manage their leads? I have been generating a lot of online leads lately through Craigslist using squeeze page websites and they are starting to stack up in my inbox.

I am starting to put together a system for myself but wanted to see if anyone has any other ideas, or any tips on managing leads effectively? Any systems that are worth it?