I'm not sure this is as complicated as you guys are saying it is.. First off, for my purposes, I wouldn't need md5sums or anything like that. In fact, I don't know if it matters what's living on the target FTP folder. I just need one-way mirroring, really, and hopefully it would operate instantly (or within a minute or so) of the files being updated.

What I was thinking of would be something that would live on my PC, and keep track of the modification times of the files that constitute a given site. When it detects that one of them has changed (modification time has changed) it sends the file to the target FTP site. That's all. I can probably script something myself, but thought something might exist already. Apparently my needs aren't as common as I thought.

The reason I'm not doing this one-file-at-a-time is that often times I'll change six different pages and have to go into an FTP program and select them individually. Uploading the entire site each time is overkill for this, but going and finding each of the files is a hassle. Ideally I'd run my own sites on my own servers, but I don't have the upsteam bandwidth for it on my cable modem.