I've been using http://karmacrm.com and I like it so far. A little minimal on functionality, but good for now (and for free). Not yet sure how I'll feel when they try to convert me to a paid account(which they've disclosed up front is on the way sometime soon).

I have been building one : http://crm.ifreetools.com - Currently in Alpha, but includes core modules.

You can also create a simple tool yourself, to match your requirements using http://creator.ifreetools.com

Applies for both CRM & Creator : - Free (ad-supported). - Works with Google Accounts or Google Apps user accounts. - Hosted over Google App Engine, custom deployment available. - Can be mapped to your sub-domain using Google Apps, for free.

Did you try SugarCRM?