AWeber is an e-mail marketing company through which any blogger or a website owner can send newsletters to it's subscribers with ease. At present, it is one of the most cheapest for e-mail marketing. It's e-mail subscription form is pretty good looking. Implementing the form in your blog will make it look more professional.
The form is basically a customised feedburner form which lets anyone subscribe to your blog RSS feed. Since the form is good looking it will catch the attention of your visitors quickly.