The long awaited Haiku R1 Alpha 4 has been released, and after a couple of major bugs discovered and squashed, a 4.1 has been released. http://www.haiku-os.org/news/2012-11-14_haiku_release_1_alpha_41
With the release of Haiku R1 Alpha1, we are now using it to build the new ports you'll see on this site. On the Downloads page you'll start seeing files with r1a1 in the file name, that indicates that it's been built and tested on Haiku R1 Alpha1. The Alpha1 image contains both gcc2 and gcc4, but defaults to using gcc2. It also includes Perl 5.10.1 and Python 2.6.2. There's also cvs, subversion, git and mercurial, so you should be able to access most repositories right out of the box.
If you are new to Haiku or have been around for years and are interested in helping out, you've come to the right place. Take a look around the site and sign up for the mailing lists. Even if you are only interested in porting one or two things, every little bit helps, so join in the fun.