I use Feedburner right now to get RSS Subscribers, but I think there is too much friction with Feedburner, they require a captcha among other things.
What are some good email RSS subscription options I can offer my readers?
If you want to pay for a service, you could try http://www.aweber.com/ or http://www.feedblitz.com/(Disclaimer: I have not used these services, I just found them online). There are probably others out there too.
Personally, I don't see what's wrong with feedburner: I use it and I have not had any problems with the captcha.
Also, try feeding your rss feed to twitter and facebook: check out twitterfeed.com. A lot of readers now a days use twitter and facebook, so that might help your website.