I created our own iscsitarget package for the time being, using a checkout of their subversion repository, since the released tarballs don't play nice with 2.6.37. That build is in the pipeline behind a handful of others, but should be available tomorrow in the testing repository.
If you're not already running on testing, here is the post describing how to switch.
Then just pacman -S iscsitarget-svn
This package incorporates both the kernel modules (compiled against latest 2.6.37.1 in testing) and userspace utilities. It's the same source and files that other distributions use, so my previously mentioned guide on howtoforge is applicable. I haven't tested this myself, so I have no idea if it even works, or how well. Any feedback you can give me on it would be great.