I fear you will get plenty of conflicting answers, everyone has their own favourite.

A lot depends on what you know already, what you have at work/school/univerity and what the people around you are using.

I've used RedHat at home and at work for a number of years. I don't hate it, but I'd have to say that I don't think it's the best thing since sliced bread. SuSE is another popular mass-market distro with a strong "enterprise" support angle, it's also supposed to be more popular in Europe than RedHat.

There are a host of smaller distros which have gone for niche market, and got good reputations in thier space. Mandrake, Lindows, Xandros all have good reputations for slick user interface and good desktop functionality.

There also the so called more "geek" distros, such as Slackware and Debian, these have a reputation for being awkward to install, but once running they are fine and dependable. There is also the ultimates, such as LFS and Gentoo, where you can build everything from scratch, and configure your system exactly as you want.

There are also some nice Linux on a CD distros, where you can boot from a CD, test things out and see if it's for you, without even having to do anything to the system!

Although not strictly Linux, don't rule out the BSD family, they offer similar functionaility with similar tools on similar hardware. If you want a ready made BSD system then look no further than a Mac, running OSX. You can probably also pick up second hand UNIX/RISC hardware very cheap, and run either it's original Unix or a Linux/BSD distro on that!

If you have never installed Linux before then I'd say join a Linux User Group, and a Perl Mongers Group for good measure. Get someone to help, and have a go, and I'd suggest a "boxed" distro first, though with time you may migrate to a more geeky version like Debian.