Check out Mailchimp. They did research on which subject lines got the best and worst open rates.

Top 5

1. [COMPANYNAME] Sales & Marketing Newsletter
2. Eye on the [COMPANYNAME] Update (Oct 31 – Nov 4)
3. [COMPANYNAME] Staff Shirts & Photos
4. [COMPANYNAME] May 2005 News Bulletin!
5. [COMPANYNAME] Newsletter – February 2006

Worst 5

1. Last Minute Gift – We Have The Answer
2. Valentines – Shop Early & Save 10%
3. Give a Gift Certificate this Holiday
4. Valentine’s Day Salon and Spa Specials!
5. Gift Certificates – Easy & Elegant Giving – Let Them Choose

What is their advice?

This is going to sound “stupid simple” to a lot of people, but here goes: Your subject line should (drum roll please): Describe the subject of your email. Yep, that’s it.

This doesn’t address conversion rates, but it does give an idea of how to get your E-mail read. People are innoculated against advertising which the worst 5 prove easily.