Tips on segmenting data for email marketing?

I regularly export my opt-in customer list from zencart for use with an email marketing service. I want to start segmenting my subscribers by segments such as recency, order frequency, amount spent, and product categories purchased in.

I've started doing this with SQL queries and spreadsheets, but it's time consuming. Is there a software package that will help me with this? Not something made for zencart necessarily, but maybe something I can import order data into and then start segmenting the list out with lots of provided filters and generate CSV files to use with my marketing service.

Or else is there an email marketing service that will do this type of thing well? I currently use VerticalResponse, and their segmentation tools don't seem to be all that great. Or maybe I'm underestimating them, because I currently only import customer name and email into their database. What do most people do?

I have a separate system ( oracle express ,free version ) connecting to zencart store , doing the analytical queries . Then I use a cron job to send to the customers the newsletter or cart abbandon or birtday emails .
I have to admin that I like challanges .. If you need help let me know .

Thanks for the reply. I went ahead and made a bunch of SQL queries to work with the database zencart is in. I think that's easiest.