Happy Grasshopper isn't a CRM, it's a simple, and easy to use way of keeping in touch with current and past clients. HG develops a series of emails each month on interesting topics. All you have to do is approve one of them and it automatically goes out to your contact list.
Whenever a HG email goes out, I'll receive several comments from people on my contact list. The emails aren't real estate related, but they do keep you top of mind in from of your clients.
Simple, inexpensive, and popular...Happy Grasshopper is a great product to keep top of mind in front of your clients.