Free AutoResponder For Low Traffic?

Only downside is that opt-ins have to view an ad before the sign up finishes (or is it right after, can't remember). And yes, I know - Gary Ambrose is a great guy and defends this on WF all the time. But just so you know. Sign up to your own list to see what your list members would see.

There are some bigger guys that offer free AR up to x number of opt-ins:
ResponseMagic - Free Email Marketing Software Systems | Tracking | Reports | Small Business | B2B (up to 100)
Benchmark - Email Marketing Pricing Plans | Benchmark Email (up to 2,000)
Vertical Response - Pricing (up to 1,000)

There are lots of free ARs, just do a search. Some though, I wouldn't want to use. You want to be as sure as possible that your emails are not going to end up in junk folders, or never get through at all.