How large is your email list? I used to just use my email client (outlook express or mozilla thunderbird) to send my newsletters out - I did that for 4 years. Now I use Vertical Response, which is in the "nearly free" category. I paid $15 for 1000 emails and with every newsletter I send out, they deduct that amount of newsletters and let me know how many I have remaining. If I send to the whole group, I have 900 remaining....then next week I send out something to the "waiting list" group of 10 people, I have 890 remaining, etc. There is no monthly charge, and they have forums and lots of helps, some free webinars, etc.
The no monthly payment and very low per-email sent was the reason I tried it. It's easy to use and very inexpensive.