Debain and
Slackware are the stable ones and being maintained by a few people, while 'big' distros like Ubuntu are maintained by people, whom real identities you'll probably never know.
You can download them right from the official sites above.
Debian has an packet manager which makes it easier to keep your distro updated and safe from harm.
Slackware developers is a team of skilled hackers who choose very solid software versions to put in a distro releases, slackware can be safe until the next release without updating.
It's from my personal experience.
