In this day and age of VMs and high bandwidth connections, I've downloaded quite a few ISOs (or grabbed a few from Linux Format) and at least poked around a little. I've tried Sabyon (?), Mandriva, Damn Small Linux, Puppy Linux, Mint, Knoppix. But the one's I actually do anything useful on are as follows in order Slackware (floppy) -> Redhat (floppy to CD to DVD) -> Fedora (CD to DVD) -> CentOS -> Ubuntu I develop seriously on CentOS and Fedora. Redhat was painful to develop on up until 5.0 then settled down and became more standardized.