There are two companies I currently use and recommend for small businesses:

1. CONSTANT CONTACT
PROS: great for small lists, easy to use, good selection of templates, import your contacts easily
CONS: gets costly with big lists
Try Constant Contact - FREE 60-Day Trial.


2. AWEBER
PROS: bit cheaper for larger lists, easy to use templates; great webforms to build list - including pop-ups and hovers, integrate with your blogs and twitter accounts
CONS: after import - every subscriber must reconfirm - so you may lose some
Check out Aweber now