The ones built into Plesk and cPanel are pretty damned good, although Plesk takes the biscuit, I think. Although, I sense that isn't exactly what you were looking for? I don't know any web-based autoresponders, but I do know how to setup outlook express for it [PS,, 400th post]
The problem as I see it is that if you want to move to a move robust autoresponder in the future they will not allow you to import a list or they will allow you but will force each added name to re-optin when added. So they way I see it the autoresponder thing is a $20 per month cost (Aweber or something like that) which is minimal for future gains if you plan on being in the internet marketing game for a while.
You can look into http://infinite.ibasics.biz/ or http://phplist.com, you would need to have a hosting service and i do have phplist on my blog which collects the emails. Still having issues sending out emails though so i would have to look into it further so tech knowledge is a plus when installing.
Hmmm. (Scratching my head) There seems to be an opinion here that free auto-responders aren't very good. I have to agree. You get what you pay for in this world, you know?
I don't know, it seems to me the majority of the web is built upon an Open Source operating system and it runs pretty well... I'd agree in relation to this thread that there's a sever lacking among freeware/open source auto-responders at the moment, but even with their limitations there are some decent options still available. Infinite (linked in another reply above) is one I've used and been happy with. PHPList also seemed decent, though I had a horrible time customizing it at all when I tried it out so I haven't used it in a production environment. If I remember correctly, freeautobot hosts your list on their servers? I've never tried it but I seem to recall that was the case when I looked it over in the past, and if I'm right that's why I didn't use it. The one problem with a free or open source option in my opinion is the reality that those behind it may walk away eventually, so I'd never use one that held my data outside of my servers.