I highly recommend staying away from Exact Target / Sales Force. I worked with them for a year and their customer service is terrible and solutions very dated. One that I would recommend is Bronto. You will want to look for a complete solution unless you have developers on hand to build emails, configure them, and deploy them. Services like sendgrid are just an API. You have to create the templates from hand and deploy them all manually through their API. Where as Bronto is a full service solution for email campaigns. I think Mailchimp is a similar full service solution though that is one I've never used.