Hi Lisa,
Just what features are you looking for in an autoresponder?
I'm pretty familiar with the offerings from Constant Contact, 1Shoppingcart and Aweber - and they all seem to fill different niches in the industry.
Constant Contact is great if you want to send nice looking HTML newsletters as they provide some nice looking templates (of course you can also send plain text too) - but they're not really an autoresponder service, as you can't set up a series of messages to be sent over time to someone.
1shoppingcart is another great service that makes it easy to setup autoresponders, but they don't offer any templates if you want to do HTML emails. I started out using them earlier this year at about $19 a month, but then they upped their prices and lost me to Aweber.
I've been using Aweber for a few months and for $19 a month you get a pretty full featured service to use. They make it easy to send both broadcast messages and autoresponders, but like 1Shoppingcart you're on your own if you want to setup HTML emails.
In regards to your catalog question, most autoresponder services give you the ability to sign people up for one autoresponder when they sign up for another - so you should be able to have people that sign up for a catalog added to your newsletter list. Of course you'll want to let them know that signing up for a catalog will place them on the other list so they don't cry "spam" when they start getting emails from you.
Steve
P.S. Just out of curiosity, what's the "IBF site builder?"