http://www.zoho.com is the one I have been using recently, but unfortunately I don't have much experience with Salesforce to make a proper comparison.

I've heard good things about this service (haven't used it though): https://getbase.com/

There are so many options! One that a friend of mine has put together is - http://getmysky.com/

I really like http://www.karmacrm.com - probably should have included that in my list

Capsule CRM - www.capsulecrm.com